Tyler Brennan v. Stephen Dickson

United States Court of Appeals
FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued December 15, 2021 Decided July 29, 2022

No. 21-1087

TYLER BRENNAN AND RACEDAYQUADS LLC,
PETITIONERS

v.

STEPHEN DICKSON, ADMINISTRATOR AND FEDERAL AVIATION
ADMINISTRATION,
RESPONDENTS

On Petition for Review of an Order
of the Federal Aviation Administration

Jonathan Rupprecht argued the cause for petitioners. With
him on the briefs were Elizabeth Candelario and Kathleen
Yodice.

Casen B. Ross, Attorney, U.S. Department of Justice,
argued the cause for respondents. With him on the brief were
Brian M. Boynton, Acting Assistant Attorney General, Michael
S. Raab, Attorney, John E. Putnam, Acting General Counsel,
U.S. Department of Transportation, Paul M. Geier, Assistant
General Counsel, and Charles E. Enloe, Trial Attorney.
 2
Joshua S. Turner and Sara M. Baxenberg were on the brief
for amicus curiae the Association for Unmanned Vehicle
Systems International in support of respondents.

Before: PILLARD, WILKINS and WALKER, Circuit Judges.

Opinion for the Court filed by Circuit Judge PILLARD.

PILLARD, Circuit Judge: Drones are coming. Lots of
them. They are fun and useful. But their ability to pry, spy,
crash, and drop things poses real risks. Free-for-all drone use
threatens air traffic, people and things on the ground, and even
national security. Congress recognizes as much. It passed a
law in 2016 requiring the Federal Aviation Administration
(FAA) to “develop[] . . . consensus standards for remotely
identifying operators and owners of unmanned aircraft
systems” and to “issue regulations or guidance, as appropriate,
based on any standards developed.” FAA Extension, Safety,
and Security Act of 2016 (FAA Extension Act), Pub. L. No.
114-190, § 2202(a), (d), 130 Stat. 615, 629 (2016). And in
2018, Congress extended the FAA’s authority over small
recreational drones. FAA Reauthorization Act of 2018, Pub.
L. No. 115-254, § 349(f)(3), 132 Stat. 3186, 3299 (2018). In
response to Congress’s call to prioritize the development of
capacities to increase airspace awareness and promptly
mitigate threats as a means to protect the safety and security of
U.S. airspace, the FAA promulgated the Remote Identification
(Remote ID) Rule challenged here.

Remote ID technology requires drones in flight to emit
publicly readable radio signals reflecting certain identifying
information, including their serial number, location, and
performance information. Those signals can be received, and
the Remote ID information read, by smart phones and similar
devices using a downloadable application available to the
 3
FAA, government entities, and members of the public,
including other aircraft operators. The FAA likens Remote ID
to a “digital license plate.” Remote Identification of
Unmanned Aircraft (Final Rule or Remote ID Rule), 86 Fed.
Reg. 4390, 4396 (Jan. 15, 2021); FAA Br. at 17. Like a license
plate, Remote ID acts as a basic building block of regulatory
compliance by attaching a unique, visible, yet generally
anonymous identifier to each device in public circulation.
Unlike a license plate on the back of a car, however, Remote
ID is detectible in real time only when the drone is moving.
Also unlike a vehicle’s license plate, which can only be read by
the naked eye from a few yards away, a Remote ID message
can be “read” by people within range of local radio signals yet
not near enough even to see the drone itself.

The FAA separately obtains certain nonpublic personally
identifying information from drone owners as a requisite of
their unmanned aircraft registrations, and that information is
protected by the Privacy Act, 5 U.S.C. § 552a. A Remote ID
message may only be matched to that nonpublic information
and used by the FAA or disclosed to law enforcement outside
of the FAA “when necessary and relevant to a[n] FAA
enforcement activity,” Privacy Act of 1974; System of Records
Notice, 81 Fed. Reg. 54,187, 54,189 (Aug. 15, 2016), and even
then it is subject to “all due process and other legal and
constitutional requirements,” Final Rule, 86 Fed. Reg. at 4433.
The Rule does not otherwise authorize private or public actors
access to drone owners’ or pilots’ nonpublic personally
identifying information, id. at 4433-34, nor does it permit or
contemplate storage of Remote ID data for subsequent record
searches.

Petitioners Tyler Brennan, a drone user, and
RaceDayQuads, the drone retailer Brennan owns (referred to
jointly as Brennan), want the Rule vacated. Brennan asserts
 4
that the Rule’s Remote ID requirement amounts to constant,
warrantless governmental surveillance in violation of the
Fourth Amendment. His request for vacatur of the Rule,
amounting to a facial challenge, must fail because drones are
virtually always flown in public. Requiring a drone to show its
location and that of its operator while the drone is aloft in the
open air violates no reasonable expectation of privacy.
Brennan hypothesizes that law enforcement authorities could
use Remote ID to carry out continuous surveillance of drone
pilots’ public locations amounting to a constitutionally
cognizable search, or that the Rule could be applied in ways
that would reveal an operator’s identity and location at a home
or in an otherwise private place. But he has not shown that any
such uses of Remote ID have either harmed him or imminently
will do so, thus he presents no currently justiciable, as-applied
challenge.

Brennan also claims that the Remote ID Rule must be
vacated due to various procedural missteps he believes the
FAA made in promulgating it. But none of those asserted flaws
affects the validity of the Rule. The communications that
Brennan challenges as ex parte did not materially bear on the
rulemaking, so their exclusion from the administrative record
did not interfere with the requisite opportunity for public
comment. The Final Rule’s provisions for altitude
measurement using geometric pressure and retrofitting of
existing unmanned aircraft equipment are logical outgrowths
of the Proposed Rule on which the public was able to—and
did—comment. The FAA also fulfilled the statutory directive
that it consult with the Radio Technical Commission for
Aeronautics, Inc. (RTCA), the National Institute of Standards
and Technology (NIST), and industry stakeholders. Finally,
Brennan faults the FAA for not adequately addressing certain
comments, but the FAA need not respond to purely speculative
comments, and its consideration of about 53,000 public
 5
comments and detailed explanation of the policy choices in the
Final Rule fully met its obligation under the Administrative
Procedure Act (APA).

We accordingly deny the petition.

BACKGROUND

I. Factual context of the Final Rule

The Remote ID Rule responds to the development of
sophisticated yet inexpensive drone equipment, which “has
allowed for hundreds of thousands of new operators to enter
the aviation community.” Final Rule, 86 Fed. Reg. at 4395.
Drones’ growing accessibility has unlocked a large recreational
market for both factory- and home-made models: Of the
865,505 drones registered with the FAA by mid-2022, 538,172
were for recreational use. See Drones by the Numbers, FAA
(May 31, 2022),
https://www.faa.gov/uas/resources/by_the_numbers/.
Meanwhile, rapidly accelerating commercial uses and planned
uses of drones include infrastructure inspection, real estate
photography, and agriculture management. Universities use
them for research activities. The healthcare industry uses
drones to deliver medical supplies, whether to quickly traverse
high-congestion cities or to reach remote areas lacking other
viable transport. Governments at every level increasingly rely
on drones’ distinctive capabilities for tasks ranging from
search-and-rescue missions to border patrol. Public and private
emergency responders alike use drones to observe hard-to-
reach accident sites, monitor natural disasters, and assist in
rescue and recovery. See Amicus Br. of the Ass’n for
Unmanned Vehicle Sys. Int’l at 5. And plans are afoot for
major expansions of other, routine drone uses such as express
 6
package shipping and delivery. E.g., Final Rule, 86 Fed. Reg.
at 4481.

All the while, increasing drone usage creates more air
traffic. And the features that make drones so popular present
novel and complex challenges to a smooth integration of
drones into the 29 million square miles of U.S. airspace that
tens of thousands of commercial and private aircraft share each
day. Congestion increases risks of drone collisions with other
aircraft, especially helicopters or agricultural aircraft flying at
low altitudes, and aircraft taking off or landing at airports,
landing strips, or heliports. The established U.S. air traffic
control system depends on constant lines of communication
between traffic controllers and pilots in flight to avert risks to
aircraft and to people and property on the ground. But drones
have no operator on board to receive or transmit air-traffic
communications, nor do they communicate with a centralized
FAA tower to coordinate with nearby aircraft. Without Remote
ID, pilots must rely solely on visual inspection of the sky to
avoid collisions with drones, and manned aircraft are likewise
left without electronic data on the locations of any drones
flying in their vicinity. Drones’ technical capability of flying
at night, over people, and beyond their operators’ lines of sight
pose additional risks associated with a lack of situational
awareness, including collision with other aircraft or objects,
falling on and injuring people, and straying into private or
sensitive areas. Safety concerns pertaining to national security
and law enforcement are intensified when unidentified drones
of unknown origin and intent fly over airports, public facilities,
energy production infrastructure, sports stadiums, or other
open-air venues where the concentration of people is high or
the ability to damage things and disrupt daily life is significant.
See, e.g., Remote Identification of Unmanned Aircraft Systems
 7
(Proposed Rule), 84 Fed. Reg. 72,438, 72,455 & nn.22, 26
(proposed Dec. 31, 2019). 1

Drones in flight are also difficult to identify with the naked
eye. Prior regulations required the exterior of all small drones
flown in U.S. airspace to be marked with the device’s
registration number. See 14 C.F.R. §§ 48.200, 48.205 (2021).
But a number physically marked on a drone itself “is only
visible upon close inspection, making visual identification of
unmanned aircraft in flight difficult or impossible.” Final Rule,
86 Fed. Reg. at 4397. The known difficulty of identifying
drones from afar increases the likelihood that drone operators
will engage in reckless, prying, or aggressive behavior under
cover of anonymity. Unseen and potentially untraceable
operators may fly drones in uncoordinated, intrusive, or unsafe
ways.

Errant drone flights are not unusual: In 2019, the FAA
alone received an average of six reports daily from people who
claimed to have witnessed unauthorized drone operations.
Proposed Rule, 84 Fed. Reg. at 72,455. The FAA has noted
the potential use of drones for illegal activities, including
“carrying and smuggling of controlled substances, illicit drugs,
and other dangerous or hazardous payloads; the unlawful
invasion of privacy; illegal surveillance and reconnaissance;
the weaponization of [drones]; sabotaging of critical

1
Citing Scott Gleeson, Juvenile Was Operating the Drone that Flew
Over Fenway Park in Red Sox Game, Police Say, USA TODAY (Apr.
13, 2019),
https://www.usatoday.com/story/sports/mlb/redsox/2019/04/13/dro
ne-fenway-park-juvenile/3457190002/; Lori Aratani, Drone Activity
Halts Air Traffic at Newark Liberty International Airport, WASH.
POST (Jan. 22, 2019),
https://www.washingtonpost.com/transportation/2019/01/22/drone-
activity-halts-air-traffic-newark-liberty-international-airport/.
 8
infrastructure; property theft; disruption; and harassment.” Id.
at 72,454. Extremists have increasingly sought to use drones
to carry out violent attacks: Terrorists killed several people by
detonating a bomb carried by a drone that flew above a military
parade in Yemen. Id. at 72,455 & n.34. 2 The Islamic State and
other terrorist organizations have reportedly modified
commercially available drones so they can carry and release
munitions and explosives. Id. at 72,455 & n.31. 3 A would-be
assassin used a drone to target then-President Nicolás Maduro
in Venezuela. Id. at 72,455 & n.32.4 And British intelligence
agencies uncovered a terrorist plan to fly drones into the
engines of commercial airplanes as they took off from airports
in the United Kingdom. Id. at 72,455 & n.33. 5

II. Legal context of the Final Rule

Congress has responded to the rapid proliferation of
drones, and the unique challenges they pose, by enacting laws
to guide a safe and efficient transition to a new chapter in U.S.
airspace use. It defined an “unmanned aircraft,” or drone, as
2
Citing Houthi Drones Kill Several at Yemeni Military Parade,
REUTERS (Jan. 10, 2019), https://www.reuters.com/article/us-
yemen-security/houthi-drones-kill-several-at-yemei-military-
parade-idUSKCN1P40N9.
3
Citing Don Rassler, The Islamic State and Drones: Supply, Scale,
and Future Threats, COMBATING TERRORISM CTR. AT WEST POINT,
at iv (July 2018), https://ctc.usma.edu/wp-
content/uploads/2018/07/Islamic-State-and-Drones-Release-
Version.pdf.
4
Citing Venezuela President Maduro Survives ‘Drone Assassination
Attempt’, BBC (Aug. 5, 2018), https://www.bbc.com/news/world-
latin-america-45073385.
5
Citing Patrick Williams, Terror Drone Plot FOILED: Brit Spies
Stop Plan to Bring Down AIRLINER, DAILY STAR (Aug. 19, 2018),
https://www.dailystar.co.uk/news/latest-news/terror-drone-plot-
britain-uk-16886096.
 9
“an aircraft that is operated without the possibility of direct
human intervention from within or on the aircraft,” 49 U.S.C.
§ 44801(11), plus the aircraft’s system of “associated elements
(including communication links and the components that
control the unmanned aircraft) that are required for the operator
to operate safely and efficiently in the national airspace
system,” id. § 44801(12).

The United States Government “has exclusive sovereignty
of airspace of the United States,” and the FAA is
congressionally empowered to “develop plans and policy for
the use of the navigable airspace and assign by regulation or
order the use of the airspace necessary to ensure the safety of
aircraft and the efficient use of airspace.” Id. § 40103(a)(1),
(b)(1). The navigable airspace of the United States includes
airspace above minimum flight altitudes and the airspace
necessary for safe takeoff and landing of aircraft. Id.
§ 40102(a)(32). Federal law calls on the FAA to

prescribe air traffic regulations on the flight of
aircraft (including regulations on safe altitudes)
for—

(A) navigating, protecting, and identifying
aircraft;

(B) protecting individuals and property on the
ground;

(C) using the navigable airspace efficiently; and

(D) preventing collision between aircraft,
between aircraft and land or water vehicles,
and between aircraft and airborne objects.
 10
Id. § 40103(b)(2). The agency must also “promote safe flight
of civil aircraft in air commerce by prescribing . . . regulations
and minimum standards for other practices, methods, and
procedure the Administrator finds necessary for safety in air
commerce and national security.” Id. § 44701(a), (a)(5).

In late 2011, Congress directed the FAA to establish drone
test sites, see National Defense Authorization Act for Fiscal
Year 2012, Pub. L. No. 112-81, § 1097, 125 Stat. 1298, 1608-
09 (2011) (codified at 49 U.S.C. § 40101 note), and in 2012 it
called on the FAA to create a system to regulate the operation
of small civil (i.e. nongovernmental) drones to integrate them
into national airspace, see FAA Modernization and Reform Act
of 2012, Pub. L. No. 112-95, §§ 332, 333, 126 Stat. 11, 73-76
(2012). The FAA then promulgated a comprehensive set of
regulations for routine use of small, unmanned aircraft in 2016.
14 C.F.R. pt. 107. At first, Congress expressly excluded model
aircraft, or small drones used strictly for hobby or recreational
use, from its call for drone regulation. See FAA Modernization
and Reform Act, § 336(a), 126 Stat. at 77 (providing that the
FAA “may not promulgate any rule or regulation regarding a
model aircraft”); Taylor v. Huerta, 856 F.3d 1089, 1092 (D.C.
Cir. 2017).

But rapidly increasing drone use and the associated
complexities prompted further congressional action, laying the
foundation for the rule at issue here: The FAA Extension Act
of 2016 directed the FAA to develop the capacity to remotely
locate drones in flight and contact their operators as needed to
ensure regulatory compliance. See FAA Extension Act,
§ 2202(a), 130 Stat. at 629. In particular, the Act required the
FAA to report to the relevant congressional committee on any
remote identification standards developed within one year of
the Act, and then issue appropriate regulations or guidance no
later than one year after the report. Id. § 2202(c)-(d), 130 Stat.
 11
at 629. And in the FAA Reauthorization Act of 2018, Congress
tightly curtailed the statutory exception for small hobbyist
drones and made clear that they are generally subject to the
same rules regarding registration and marking, remote
identification, and “maintaining the safety and security of the
national airspace system” as applied to other unmanned aircraft
and unmanned aircraft systems. FAA Reauthorization Act,
§ 349(a), (b), (f), 132 Stat. at 3297; 49 U.S.C. § 44809(f); see
Final Rule, 86 Fed. Reg. at 4403.

III. The Remote ID Rule

The FAA complied with Congress’s call for a regulatory
system of remote identification of drones and their pilots by
promulgating the Remote ID Rule in January 2021. By
developing a general requirement that drones be capable of
Remote ID, the FAA aimed to “provide airspace awareness to
the FAA, national security agencies, law enforcement entities,
and other government officials.” Final Rule, 86 Fed. Reg. at
4393. In the face of increasing drone use in U.S. airspace, the
FAA sought a means “to distinguish compliant airspace users
from those potentially posing a safety or security risk.” Id. at
4395; accord FAA Br. at 7.

Remote ID promises “greater situational awareness of
[drone] operations to airport operators and other aircraft in the
vicinity of those operations” that enables the FAA to safely
accommodate drone flight together with low-altitude flight of
manned aircraft. Final Rule, 86 Fed. Reg. at 4488. The FAA
predicted that near-real-time Remote ID would “enhance threat
assessments” and “discourage[] unsafe flying by operators of
unmanned aircraft, thereby promoting safety for other users of
the airspace of the United States and for those on the ground.”
Id. at 4490. According to the FAA, the Remote ID Rule
advances its mission to “promot[e] the safe and efficient use of
 12
the navigable airspace” by “strengthen[ing] the FAA’s
oversight of [drone] operations and support[ing] efforts of law
enforcement to address and mitigate disruptive behavior and
hazards, which may threaten the safety and security of [U.S.]
airspace.” Id. at 4493. Identifying drone operators “enable[s]
better threat discrimination, an immediate and appropriate law
enforcement response, and a more effective follow-on
investigation.” Id. at 4435.

The Remote ID Rule is the product of a year-long public
rulemaking in which the agency received approximately
53,000 comments. See Proposed Rule, 84 Fed. Reg. 72,438
(proposed Dec. 31, 2019). Its Remote ID requirement becomes
effective on September 16, 2023, Final Rule, 86 Fed. Reg. at
4390, and it requires nonmilitary drones weighing over 0.55
pounds and registered with the FAA to signal identifying
information during flight, id. at 4403, 4505. Drones subject to
the Rule must use unlicensed, publicly accessible local radio
frequencies and remain in compliance with the Remote ID
requirements. The Rule does not allow disabling of Remote ID
functions, and if a drone experiences Remote ID failure or
malfunction, its operator must land the device as soon as
practicable.

Drones must emit the Remote ID signal while the drone is
in flight, from its takeoff to shutdown; the requirement is
inapplicable while the drone is “entirely indoors, underground,
or inside an enclosed space such as a netted enclosure.” Id. at
4404. All broadcasts are local and use unlicensed radio
frequency spectrum that smart devices, like smart phones,
tablets, or similar commercially available devices, can receive
“within a limited proximity.” Id. at 4428. The FAA and
anyone with the proper equipment nearby will be able to
receive those signals in real time during the drone’s flight. The
Rule “does not contemplate the FAA’s routine collection or
 13
retention of broadcast information. At this time, the FAA does
not have plans to collect or retain the broadcast information.”
U.S. DEP’T OF TRANSP., PRIVACY IMPACT STATEMENT – FAA,
REMOTE IDENTIFICATION OF UNMANNED AIRCRAFT FINAL
RULE at 10 (2021), J.A. 221.

The Rule specifies three categories of Rule-compliant
drones based on their Remote ID capabilities. Standard
Remote ID drones are commercially manufactured drones,
which, as of September 16, 2022, must be designed and
produced to emit radio signals directly from the drone in flight.
Broadcast Module drones are those built before September 16,
2022, without Remote ID capacity, which are retrofitted with a
module to enable that capacity in compliance with the Rule;
once modified, they may only be flown within the operator’s
line of sight. Unidentified drones without any Remote ID
capability may only fly within the drone pilot’s sight within
FAA-recognized identification areas, or ID Areas—specific
geographic areas set aside by the FAA for recreational or
educational drone flight. Community-based organizations and
educational institutions, including primary and secondary
schools, trade schools, colleges, and universities, may apply to
the FAA for ID-Area status.

A Standard Remote ID drone in flight must continuously
emit: (1) its unique identification number; (2) its latitude,
longitude, geometric altitude, and velocity; (3) the latitude,
longitude, and geometric altitude of the drone’s control station;
(4) a time mark; and (5) any applicable “emergency status”
indication (downed aircraft, low fuel, low battery, or other
abnormal drone status not apparent from the nonemergency
information or the drone’s appearance). Final Rule, 86 Fed.
Reg. at 4410, 4412, 4423. Retrofitted Broadcast Module
drones must generally share the same information, except that,
in keeping with reasonable limits on retrofit technology, they
 14
only need identify the drone’s takeoff location, not its control
center’s location throughout the drone’s flight nor its
emergency status.

The unique identification number referenced by the Rule
is the drone’s serial number. A drone owner must register the
serial number with the FAA, along with the owner’s name and
contact information, to enable the FAA to identify and contact
owners and hold them personally accountable for their aircraft.
See 14 C.F.R. § 48.110 (required drone registration data); id.
§ 48.15 (requirement to register drones); see also 49 U.S.C.
§ 44102 (aircraft registration requirements). But serial
numbers are not generally available to the public. Access to
owners’ personally identifying information contained in FAA
registration records is “strictly limited to authorized FAA and
other government and law enforcement personnel who are
operating in their official capacities pursuant to all legal
limitations and authorized use of the information,” including
legal and constitutional requirements. Final Rule, 86 Fed. Reg.
at 4433. Federal, state, and local law enforcement personnel,
like any member of the general public, can receive Remote ID
messages, but the Rule does not authorize anyone other than
personnel engaged in FAA enforcement activity to access
individuals’ drone registration data. See FAA Br. at 12-13, 31
n.4. While the Rule refers to potential future uses of Remote
ID information by law enforcement, the FAA has not addressed
the circumstances under which accredited and verified law
enforcement personnel and federal agencies might access
drone operators’ identifying information, other than to reiterate
that legal and constitutional limits would apply.

IV. The petition for review

Tyler Brennan is an Air Force pilot and self-proclaimed
“avid drone user.” Pet. Br. at 16. He describes his company,
 15
RaceDayQuads, as a “one stop drone shop” that sells drones
and drone parts and offers technical support.
RACEDAYQUADS, https://www.racedayquads.com/ (last
visited July 26, 2022). RaceDayQuads, says Brennan, has
served more than 40,000 different customers per year in its
almost four years of existence. Again, for convenience we
jointly refer to owner and company as Brennan.

Brennan seeks review and vacatur of the Final Rule. He
argues that the location tracking required by the Remote ID
Rule infringes a drone operator’s reasonable expectation of
privacy so constitutes a warrantless search in violation of the
Fourth Amendment. He also claims that the Final Rule is
arbitrary and capricious on four grounds: (1) the FAA
impermissibly relied on ex parte communications during the
rulemaking that were not in the administrative record nor
available for public comment; (2) aspects of the Final Rule
were not logical outgrowths of the Proposed Rule; (3) the FAA
failed to comply with a statutory requirement to consult with
specified entities in formulating standards; and (4) the FAA
failed to address material comments. The petition is timely and
49 U.S.C. § 46110(a) grants us jurisdiction to review.

DISCUSSION

As every pilot knows, Congress has authorized the Federal
Aviation Administration to regulate the public airspace of the
United States. FAA regulation enables safe and efficient
shared use of the skies by government, commercial aviation,
and private pilots. Most existing aviation rules are inapplicable
to drones, but the Rule at issue here is specially fashioned at
the behest of Congress to ensure that even drone pilots shoulder
the baseline responsibility of reciprocal airspace awareness: At
a minimum, drone pilots must enable other pilots and people
on the ground who may be affected by their drones to discern
 16
their location during flight. Remote ID provides that direct link
between the drone and its pilot and enables accountability of
drone pilots analogous to that of pilots collocated with manned
aircraft. Final Rule, 86 Fed. Reg. at 4419. For the following
reasons, we conclude that Brennan has failed to show that the
Remote ID Rule violates the Fourth Amendment, and that his
procedural challenges likewise lack merit.

I. Fourth Amendment claim

It is hard to see what could be private about flying a drone
in the open air. Activities that require privacy are not typically
conducted aloft; in contrast to how we use our homes, cars, and
cell phones, people do not ordinarily live in or store private
objects or information in their drones. Rather, as with cars
traveling on public streets and highways or helicopters taking
off, drones that take to the skies ordinarily make themselves
visible to onlookers. And a drone pilot who elects to fly
outdoors puts an aircraft into airspace used by rapidly
increasing numbers of other new users—both other aircraft
piloted remotely and myriad aircraft taking off or landing with
pilots aboard.

Brennan claims that the Rule interferes with his reasonable
expectation of privacy without requiring a warrant, in violation
of the “right of the people to be secure in their persons, houses,
papers, and effects, against unreasonable searches and
seizures.” U.S. CONST. amend. IV. His briefing highlights
certain potential applications of the Rule: “To be clear,” he
acknowledges, “Remote ID for recreational drones is very
much appropriate when tied to legitimate safety and security
concerns.” Pet. Br. at 20 (emphasis in original). But this Rule,
Brennan asserts, was promulgated not to protect airspace safety
but to enable the government to conduct “intrusive tracking of
everyone, everywhere, all the time, with extremely low costs
 17
and ease of accessibility for law enforcement without judicial
safeguards.” Id. at 30. Citing the Supreme Court’s Fourth
Amendment precedent on electronic searches by law
enforcement, Brennan argues that the Remote ID Rule matches
or exceeds the intrusions those cases disapproved. Id. at 27-30
(citing Carpenter v. United States, 138 S. Ct. 2206, 2218
(2018), Riley v. California, 573 U.S. 373, 385 (2014), and
United States v. Jones, 565 U.S. 400, 403 (2012); id. at 416
(Sotomayor, J., concurring)). Brennan also underscores the
special Fourth Amendment solicitude for the privacy of the
home and its curtilage, which he says the Rule invades because
drones may be “flown close to the ground and hidden from
view by vegetation and fences in a private backyard.” Pet.
Reply Br. at 5; see id. at 12-13 (citing Kyllo v. United States,
533 U.S. 27, 33 (2001)); Pet. Br. at 22-25 (citing Collins v.
Virginia, 138 S. Ct. 1663 (2018)).

The FAA responds that the Remote ID Rule does not
invade any reasonable expectation of privacy, both because
aviation is extensively regulated and because the Rule applies
only to drone flights outdoors. FAA Br. at 23-34. By the same
token that identifying the airborne location of an aircraft and
collocated pilot with a transponder is not a Fourth Amendment
search, the FAA says, using Remote ID to learn the locations
of airborne drones and their pilots invades no constitutionally
recognized privacy interest. Id. at 23-24 (citing United States
v. Bruneau, 594 F.2d 1190, 1197 (8th Cir. 1979)). Even if the
Rule did implicate constitutional privacy, the FAA contends
that the searches it contemplates are excepted from the Fourth
Amendment’s warrant requirement. FAA Br. at 21-37; see
also Griffin v. Wisconsin, 483 U.S. 868, 873 (1987) (special
needs search); New York v. Burger, 482 U.S. 691, 712 (1987)
(administrative search of “closely regulated” business).
 18
Brennan’s pre-enforcement Fourth Amendment claim
seeks wholesale vacatur of the Remote ID Rule, Pet. Br. at 20,
65, so we understand him to be challenging the Rule’s facial
validity—an unusual but not unheard-of type of Fourth
Amendment claim. See City of Los Angeles v. Patel, 576 U.S.
409, 415-16 (2015) (citing cases). To prevail, Brennan “must
establish that no set of circumstances exists under which the
[rule] would be valid.” Ass’n of Priv. Sector Colls. & Univs. v.
Duncan, 681 F.3d 427, 442 (D.C. Cir. 2012); accord United
States v. Salerno, 481 U.S. 739, 745 (1987). Identifying
potential applications of the rule that could be unlawful is not
enough. Sherley v. Sebelius, 644 F.3d 388, 397 (D.C. Cir.
2011). And because “[v]irtually every legal (or other) rule has
imperfect applications in particular circumstances,” Barnhart
v. Thomas, 540 U.S. 20, 29 (2003) (emphasis in original), we
need not—indeed, cannot—“resolve every hypothetical
presented” by Brennan, Nat’l Ass’n of Reg. Util Comm’rs v.
FERC, 964 F.3d 1177, 1188 (D.C. Cir. 2020); see also Am.
Bankers Ass’n v. Nat’l Credit Union Admin., 934 F.3d 649,
667-68 (D.C. Cir. 2019). Where a challenged rule does not
exceed statutory authority and comports with the APA, “we
will uphold the provision and preserve the right of
complainants to bring as-applied challenges against any
alleged unlawful applications.” Ass’n of Priv. Sector Colls. &
Univs., 681 F.3d at 442.

Brennan’s facial Fourth Amendment challenge fails
because drone pilots generally lack any reasonable expectation
of privacy in the location of their drone systems during flight.
A “search” for purposes of the Fourth Amendment occurs
when government action infringes a sphere an individual seeks
to preserve as private and the expectation of privacy is one
society considers reasonable under the circumstances.
Carpenter, 138 S. Ct. at 2213; Smith v. Maryland, 442 U.S.
735, 740 (1979); Katz v. United States, 389 U.S. 347, 361
 19
(1967) (Harlan, J., concurring). Brennan does not dispute the
general visibility to onlookers of drones in the sky. Drones fly
in the open, and people ordinarily lack a reasonable expectation
of privacy “for activities conducted out of doors in fields.”
Oliver v. United States, 466 U.S. 170, 178 (1984). “[O]pen
fields beyond the curtilage of a home, whether or not privately
owned, are not among the protected places and things
enumerated in the [Fourth] Amendment’s text, so they fall
outside the Fourth Amendment’s coverage.” N. Am. Butterfly
Ass’n v. Wolf, 977 F.3d 1244, 1264 (D.C. Cir. 2020)
(discussing Oliver, 466 U.S. at 176-80) (formatting modified).
And there is no reasonable expectation of privacy in the
movement of objects outside a residence where they can be
viewed from a public route or adjoining premises, United
States v. Knotts, 460 U.S. 276, 281-82 (1983), nor in activities
conducted in the curtilage of a home, even behind a hedge or
fence, if they may be viewed by “naked-eye observation” from
an “aircraft lawfully operating” above the property, California
v. Ciraolo, 476 U.S. 207, 213 (1986).

Brennan suggests pilots might use a drone’s control station
inside a home or fly the drone in its curtilage below the treeline
out of public view. But the Rule does not mandate Remote ID
for drone flights indoors, thus exempting flights inside a home,
barn, or other private building. See Final Rule, 86 Fed. Reg. at
4404. Nor does it require Remote ID for drone flights in netted
outdoor enclosures. Id. And nothing in the administrative
record establishes that drones covered by the Remote ID Rule
are usually flown from or in private spaces not visible to others,
making drone systems’ potential uses there no basis for facial
invalidation.

Sometimes government surveillance of conduct that takes
place in public can nonetheless run afoul of the Fourth
Amendment, see, e.g., Carpenter, 138 S. Ct. at 2217; Jones,
 20
565 U.S. at 405, but the Remote ID Rule does not authorize any
such privacy-invading practice. That is so for at least three
interrelated reasons.

First, the Rule calls for installation, not monitoring by law
enforcement. Owners of existing drones who fly outdoors and
beyond approved drone-recreation areas (ID Areas) must
retrofit their equipment with Remote ID broadcast modules
and, as of September 2022, commercially produced drones
must be equipped with Remote ID. See 86 Fed. Reg. at 4410-
11. Brennan does not assert that equipping unmanned aircraft
with Remote ID capability is itself a search in violation of the
Fourth Amendment. And rightly so, as the installation of a
device capable of location tracking merely creates the
“potential for an invasion of privacy.” United States v. Karo,
468 U.S. 705, 712 (1984). “It is the exploitation of
technological advances that implicates the Fourth Amendment,
not their mere existence.” Id.; see also Knotts, 460 U.S. at 284-
85. Indeed, a major planned use of the Rule does not even
involve the government reading the Remote ID message, but
rather enables unmediated pilot-to-pilot signaling among
private persons for coordinated, safe use of shared airspace.

Second, the brevity and occasional character of drone
flights and the local nature of the Remote ID message makes
the FAA’s access to location information via Remote ID unlike
the kind of “dragnet” electronic surveillance to which Brennan
objects. Pet. Reply Br. at 13. “[R]elatively short-term
monitoring of a person’s movements” in public places “accords
with expectations of privacy that our society has recognized as
reasonable.” Jones, 565 U.S. at 430 (Alito, J., concurring); see
also 565 U.S. at 412 (citing Knotts, 460 U.S. at 281). The Rule
requires drones to communicate Remote ID only from takeoff
to shutdown. 86 Fed. Reg. at 4410-12. Based on a survey it
conducted of more than 15,400 drone operators, the FAA notes
 21
that private, recreational drone pilots conduct an average of
only seven drone flights per month, totaling approximately 94
minutes of monthly flight time. FAA Br. at 29 (citing FAA,
FAA Aerospace Forecast: Fiscal Years 2020-2040 at 41-43,
https://go.usa.gov/xMqTD). Unlike a cellphone, which has
become “almost a ‘feature of human anatomy’” that “tracks
nearly exactly the movements of its owner,” Carpenter, 138 S.
Ct. at 2218, nothing in the record before us suggests that
Remote ID location information provides any such “intimate
window into a person’s life,” id. at 2217. Requiring a person
during occasional short flights to identify in real time and share
her drone system’s momentary whereabouts on a local radio
frequency says little about anything else in her life.

The limited, local, real-time information sharing the Rule
requires is a far cry from the continuous surveillance the
Supreme Court has held violates reasonable expectations of
privacy. In Carpenter, for example, the government accessed
127 days’ worth of defendants’ cell phone location data
providing “a detailed and comprehensive record of the person’s
movements,” 138 S. Ct. at 2217, amounting to “near perfect
surveillance” akin to what can be achieved by an ankle
monitor, id. at 2218. And in Jones, the privacy invasion arose
from the government surreptitiously attaching a GPS monitor
to the defendant’s car, 565 U.S. at 404 & n.2, and
“catalogu[ing] every single movement” of the car for 28 days,
565 U.S. at 430 (Alito, J., concurring in the judgment); accord
id. at 415 (Sotomayor, J., concurring). No physical trespass is
asserted here, and, unlike cell-cite location data or a GPS
tracker on a car, it is unclear how a drone system’s Remote ID
could be used to place anyone at the scene of a robbery or
follow him to a drug stash house, cf. Carpenter, 138 S. Ct. at
2212-13; Jones, 565 U.S. at 402-04, nor how it could “reflect[]
a wealth of detail” about a drone pilot’s “familial, political,
professional, religious, and sexual associations,” 565 U.S. at
 22
415 (Sotomayor, J., concurring). The drone system’s real-time
location data says nothing qualitative about the nature of the
location nor the operator’s relationship to it (e.g. whether he is
at his home). Beyond the general concerns he raises about the
intrusive capabilities of electronic surveillance, Brennan offers
no specifics about how Remote ID anonymized messaging of a
drone system’s location during flight could reveal private facts
or constitute governmental abuse in derogation of the Fourth
Amendment.

We also see no basis to conclude that the FAA or other
government actors will devote the time and resources Brennan
assumes they will to exploit the Rule to somehow conduct
extended surveillance. See, e.g., Jones, 565 U.S. at 429 & n.10
(Alito, J. concurring in the judgment) (distinguishing ease of
long-term surveillance with GPS from “exceptionally
demanding” surveillance aided by limited-range radio
transmitter that “could be lost if the police did not stay close
enough”); Obama v. Klayman, 800 F.3d 559, 567 (D.C. Cir.
2015). As a practical matter, Remote ID messages are not
readily available for collection from a centralized location but
are detectible only within the ambit of a local radio signal—
which Brennan calculates to be about a one-mile radius around
the drone. 86 Fed. Reg. at 4428; see also Pet. Br. at 26; Pet.
Reply Br. at 12. As a legal matter, despite Brennan’s
assumptions to the contrary, see Pet. Br. at 21, the Rule does
not authorize aggregation and storage of flight data for later
law-enforcement querying. The Final Rule abandoned the
internet-based Remote ID proposal requiring private service
providers to log Remote ID information from drone flights and
store it for the FAA’s later access, and the FAA has disavowed
any plans under the Final Rule to log the data. U.S. DEP’T OF
TRANSP., PRIVACY IMPACT STATEMENT at 10, J.A. 221.
 23
Third, the Rule appropriately limits access to personally
identifying information in the FAA’s possession that could be
linked to a drone’s Remote ID message to reveal who owns the
drone system. Remote ID does not reveal the pilot’s or owner’s
identity, address, phone number, or other personal information.
Rather, the message shows the drone’s unique identification
number; the latitude, longitude, and geometric altitude of the
drone and of its controller; the drone’s velocity; a time mark;
and any applicable “emergency status” alert. 86 Fed. Reg. at
4410, 4412. That information itself is anonymized. The
unique identifier—the drone’s serial number—does not
disclose who is flying the drone, whether it be the registered
owner of the device or someone else.

The Rule authorizes the FAA alone to match the drone’s
nonpublic serial number to registration information, which
includes the owner’s name and contact information, and to use
that personally identifying information only for airspace safety
and security purposes relating to the drone’s operation. The
Rule’s preamble specifies that “registration data pertaining to
individuals is protected in accordance with the requirements of
the Privacy Act (5 U.S.C. 552a).” 86 Fed. Reg. at 4433. Any
use of Remote ID data, including by law enforcement
personnel, “is bound by all Constitutional restrictions and any
other applicable legal restrictions.” Id. at 4435; accord id. at
4433.

Consistent with those limitations, the Remote ID Rule
does not, without further regulatory action, authorize law
enforcement personnel to access drone owners’ personally
identifying information separate from the FAA’s involvement.
The FAA emphasized that the Rule “does not speak to the use
of information by law enforcement agencies or how remote
identification data will be correlated with other law
enforcement data.” Id. at 4436. As the agency acknowledged,
 24
amendment of its existing recordkeeping system for personally
identifying information protected by the Privacy Act, see
Department of Transportation System of Records Notice
DOT/FAA-801, 81 Fed. Reg. 54,187 (Aug. 15, 2016), would
be required before law enforcement could access registration
information to match it with Remote ID data for uses beyond
aviation safety and security, FAA Br. at 12-13, 31 n.4. And
any new or updated System of Records must be published in
the Federal Register for notice and public comment before
implementation. See 5 U.S.C. § 552a(e)(4)(D), (e)(11).
Nothing about the Rule itself supports Brennan’s assertions
that it will be used by government in ways that violate drone
pilots’ privacy rights. To be sure, it is possible that one day
government or law enforcement collection of drone system
operation data in and of itself could violate a pilot’s
constitutionally cognizable privacy interest. But Brennan has
not shown that such data collection offends the Fourth
Amendment in every application of the Rule to the typically
very public activity of drone piloting.

Because we hold Brennan’s Fourth Amendment facial
challenge fails to establish that the Remote ID Rule requires
drone operators to submit to warrantless intrusion on their
constitutionally cognizable privacy interests, we need not and
do not here address the government’s alternative argument that
an exception to the warrant requirement applies.

We likewise express no opinion on the potential viability
of any as-applied Fourth Amendment challenge to specific
applications of the Remote ID Rule. We thus do not foreclose
the possibility of a declaratory judgment or injunctive action
by a party establishing that application of the Remote ID Rule
to its own specifically delineated drone uses would subject it to
an unconstitutional privacy deprivation. See generally Alvin
Lou Media, Inc v. FCC, 571 F.3d 1, 8 (D.C. Cir. 2009)
 25
(challenge to rule’s application permissible outside 30-day
deadline to challenge the underlying rule); Indep. Cmty.
Bankers of Am. v. Bd. of Governors of Fed. Reserve Sys., 195
F.3d 28, 34-35 (D.C. Cir. 1999) (same). Nor do we pass on the
viability of Fourth Amendment objections that might be raised
on the specific facts of enforcement actions. But Brennan does
not establish here that the putative privacy breaches he fears,
such as continuous tracking of his every movement, or
intrusion on the privacy of his home, are imminent or have yet
occurred.

Because the Remote ID Rule itself “at most authorizes—
but does not mandate or direct” the subcategory of applications
that Brennan identifies as “searches” subject to the Fourth
Amendment, his allegations are too conjectural to support
standing to challenge such application. Clapper v. Amnesty
Int’l, 568 U.S. 398, 412 (2013) (formatting modified). We may
grant declaratory relief to a petitioner facing “a threat of injury
which is sufficiently direct and immediate to constitute more
than a string of contingencies or speculative characterizations,”
Branch v. FCC, 824 F.2d 37, 41 (D.C. Cir. 1987), but no such
relief is available where key facts have not “crystallized” and
it remains to be seen whether the government will ever use the
challenged legal authority unlawfully, City of Houston v. Dep’t
of Hous. and Urb. Dev., 24 F.3d 1421, 1431 (D.C. Cir. 1994).
For the reasons already discussed, we do not read the Rule on
its face to pose a direct and immediate threat of continuous law
enforcement monitoring or intrusions on the privacy of the
home.

Because Brennan has not established here that, in every
application, the Remote ID Rule authorizes warrantless
searches in violation of a reasonable expectation of privacy
protected by the Fourth Amendment, we reject his
constitutional claim.
 26
II. Procedural claims

Brennan asserts the Remote ID Rule is arbitrary and
capricious in various ways. 5 U.S.C. § 706(2)(A). None of
those challenges succeeds.

A. No ex parte communication affected the Rule

Brennan argues that the FAA engaged in secret, ex parte
communications that shaped the Final Rule but evaded public
comment. He points to the FAA’s convening of an industry
group (the Cohort) in early 2020 to give the agency technical
advice on its proposed network-based Remote ID system, its
work with a NASA drone traffic management pilot program
simultaneously with the development of the Remote ID Rule,
and its demonstration of Remote ID capabilities to a group of
public and private observers at the Federal Bureau of
Investigation Academy. Brennan asserts that the FAA should
now be required to publish a new or supplemental notice of
proposed rulemaking to fully disclose the information he
asserts the agency drew from those interactions.

Statutory requirements of public notice and comment
ensure that rules are openly developed, subjected to effective
comment from interested parties, and judicially reviewable on
a materially complete record. “[T]he very legitimacy of
general policymaking performed by unelected administrators
depends in no small part upon the openness, accessibility, and
amenability of these officials to the needs and ideas of the
public from whom their ultimate authority derives, and upon
whom their commands must fall.” Sierra Club v. Costle, 657
F.2d 298, 400-01 (D.C. Cir. 1981). As relevant here, APA
Section 4 obligates the FAA to publish notice of its proposed
rulemakings, to “give interested persons an opportunity to
participate in the rule making” by submitting comments, to
 27
consider those comments, and then to “incorporate in the rules
adopted a concise general statement of their basis and
purpose.” 5 U.S.C. § 553(c).

The APA contains no explicit bar on ex parte
communications during a rulemaking process like this one, and
communications that do not materially influence the action
taken do not run afoul of APA requirements of notice-and-
comment rulemaking. See Vt. Yankee Nuclear Power Corp. v.
Nat. Res. Def. Council, 435 U.S. 519, 523-24 (1978); Costle,
657 F.2d at 402-03; Home Box Off., Inc. v. FCC, 567 F.2d 9,
57 (D.C. Cir. 1977). Ex parte communications may
nonetheless violate the APA if “it appears from the
administrative record under review that they may have
materially influenced the action ultimately taken.” Action for
Child.’s Television v. FCC, 564 F.2d 458, 476 (D.C. Cir. 1977).

Brennan has not shown that the Remote ID Rule was
materially affected by any ex parte influence, nor has he
identified any harm he might have suffered if it were. See id.
at 477. The Cohort the FAA convened was to advise on an
approach to Remote ID that Brennan himself opposed in his
comment and that the agency did not include in the Final Rule.
The Proposed Rule would have relied primarily on the internet
to communicate Remote ID, with private companies under
contract with the FAA acting as Unmanned Aircraft System
Service Suppliers monitoring drone flights via the internet and
collecting and storing that internet-transmitted flight data for
the FAA’s access. Proposed Rule, 84 Fed. Reg. at 72,439,
72,467-68, 72,499. “Under this concept, the aircraft’s control
station (often a mobile phone) would connect to the internet
and transmit remote identification information to a third-party
service provider.” Final Rule, 86 Fed. Reg. at 4405. During
the comment period for the Proposed Rule, the FAA convened
a Cohort of private companies with experience in remote
 28
identification of drone locations to help the agency develop
technical parameters it envisioned would be contractually
required of the Service Suppliers. See id. at 4406; see also
Proposed Rule, 84 Fed. Reg at 72,484-85. But because it
ultimately concluded that a system of real-time remote
identification relying on local radio bandwidth “will be
adequate,” id. at 4408, the FAA dropped the proposed
requirement that drones use internet for Remote ID and that the
FAA access their information as collected by Service
Suppliers.

Brennan objects that FAA staff met with the Cohort but
did not include the details of those meetings in the public
record, making it impossible for the public to comment on
them. But the FAA received and responded to thousands of
comments on the internet-based proposal. More to the point,
Brennan has not shown that information the FAA obtained
from the Cohort meetings had any material bearing on the Final
Rule. The FAA’s decision to table reliance on internet-based
transmission in favor of the simpler, cheaper, and more secure
radio-broadcast system rendered irrelevant the technical
capabilities the Cohort had been asked to consider, and the
Rule’s preamble elaborates on the many reasons supporting
that decision. Final Rule, 86 Fed. Reg. at 4405-09, 4491-92.

The FAA noted that “[t]he primary challenge with [the
internet-based] concept is its reliance on Wi-Fi or cellular
network service being available where an aircraft is flying; the
concept would not work in areas lacking cellular telephone
coverage.” Id. at 4405. Relatedly, the FAA concluded the
Final Rule’s reliance on a radio-broadcast system avoids
unnecessary costs to drone users of equipment and Wi-Fi data
plans associated with the internet-based proposal. Id. at 4406-
07, 4409. And, even where reliable internet is available and
drone pilots subscribe to it, the agency noted commenters’
 29
observation that “cellular networks are optimized to work with
ground-based equipment rather than airborne equipment,” so
they might not readily support Remote ID of drones in flight.
Id. at 4407.

Security was also a major concern with the internet-based
proposal. Based on comments explaining that tracking drone
flights via the internet would leave them vulnerable to
cyberattacks, deliberate interference, and security and data
breaches by individuals, non-State actors, and foreign
governments, the FAA was persuaded that reliance on radio
frequency would, at least initially, best serve the Remote ID
Rule’s objectives. Id. at 4406-07, 4409. The FAA concluded
that “a broadcast-only solution is sufficient, for the time being
and given the types of unmanned aircraft operations that are
currently allowed, to maintain the safety and security of the
airspace of the United States” in line with authorized
operations and airspace regulations. Id. at 4409.

Even if the Final Rule had not rendered the Cohort
superfluous, the FAA’s ground rules for Cohort meetings put
discussion of the Proposed Rule off limits; the agency directed
members who wished to comment to do so via the public
rulemaking docket. See FAA Br. at 40-41. Brennan
nonetheless contends that the Cohort must have affected the
Final Rule because the preamble mentions the Cohort’s
identification of unforeseen issues with “significant technical
and regulatory requirements that go beyond existing industry
consensus standards,” and notes “the challenge of developing
and issuing technical specifications to govern remote
identification interoperability when producers of [unmanned
aircraft systems] have not yet designed” drones with Remote
ID capability. Final Rule, 86 Fed. Reg. at 4406. But those
reported difficulties are symptomatic of more fundamental
problems that the Rule fully documents without reference to
 30
the Cohort as such—even as it cites Cohort members’ duly
submitted public comments. Id. at 4408 (citing comments of
Amazon Prime Air, Verizon, Skyward, and AirMap).

In sum, the FAA’s Final Rule relied on extensive evidence
independent of whatever it might have learned from the Cohort,
and Brennan has failed to show that the agency’s
communications with the Cohort outside the rulemaking
process had any effect on the Rule.

The two other interactions that Brennan contends
amounted to impermissible ex parte influences on the Final
Rule are even further from the mark. One was the FAA’s work
with NASA on drone traffic control, which is an important but
distinct component of the agency’s efforts to integrate safe and
efficient drone flight into the national airspace. The Remote
ID Rule did not discuss or depend on the FAA’s collaboration
with NASA regarding drone traffic management. Rather, when
Congress in the 2016 FAA Extension Act directed the FAA to
develop requirements for remote identification of drones and
drone pilots during flight, now reflected in the Remote ID Rule,
it also asked the FAA to continue ongoing research
collaboration with NASA on unmanned aircraft system traffic
management. Pub. L. No. 114-190, § 2208, 130 Stat. at 633-
34. The first phase of the traffic management study concluded
in October 2019, after the Proposed Rule’s comment period
closed; the second, pursuant to the 2018 FAA Reauthorization
Act, Pub. L. No. 115-254, § 376(b), 132 Stat. at 3314-15, tested
traffic management systems with drones remotely identified
under the Final Rule after its publication. See FAA, Unmanned
Aircraft Systems (UAS) Traffic Management (UTM) Pilot
Program (UPP): UPP Summary Report (Oct. 2019),
https://go.usa.gov/xFmVU; FAA, Unmanned Aircraft Systems
(UAS) Traffic Management (UTM) UTM Pilot Program (UPP)
Phase Two (2) Progress Report (Mar. 2021),
 31
https://go.usa.gov/xFmy9; FAA, Uncrewed Aircraft Systems
(UAS) Traffic Management (UTM) UTM Pilot Program (UPP)
Phase 2 Final Report (July 2021), https://go.usa.gov/xFmyU.
The Remote ID Rule plainly was not influenced by the asserted
ex parte input from NASA.

Finally, Brennan sees illegitimate ex parte influence in a
demonstration the FAA conducted at the FBI Academy in
Quantico to show “detect and display information about
unmanned aircraft operation below 400 feet.” FAA
Memorandum, Summary of the Technology Demonstration
Regarding Remote Identification of Unmanned Aircraft
Systems Notice of Proposed Rulemaking, Docket No. FAA-
2019-1100 (Sept. 30, 2020). Pointing to a four-page FAA
memo that describes the demonstration, which included a
question-and-answer session Brennan learned of through a
FOIA request, id.; see also Pet. Br. at 12 n.8, Brennan asserts
that the public was improperly denied notice and an
opportunity to comment on “the details of the Remote ID
demonstration for law enforcement officials, and the complete
explanation of how this data will be used and stored for law
enforcement purposes,” Pet. Br. at 37. Brennan does not
identify how he believes the demonstration or related
discussion, neither of which are mentioned in the Final Rule,
could have affected it, but his references to data use and storage
by law enforcement appear to relate to his Fourth Amendment
concerns. As already discussed, the Final Rule does not
authorize data storage nor use by non-aviation law
enforcement, and Brennan’s concerns about such eventualities
are misplaced or premature.

In sum, none of the communications Brennan identifies as
“ex parte” affected the integrity of the notice and comment
process and thus the validity under the APA of the Remote ID
Rule.
 32
B. The Final Rule was a logical outgrowth of the
Proposed Rule

Brennan asserts that two requirements of the Final Rule
“do not logically stem from the notice provided in the
[Proposed Rule], rendering those aspects of the rule void.” Pet.
Br. at 39. He objects to the change from measuring the reported
altitude of drone control stations using barometric pressure
altitude to measuring it geometrically with GPS, and to the
elimination of the internet-based “Limited Remote
Identification” option for retrofitting existing drones in favor
of the radio-broadcast module option.

To comport with the APA’s notice-and-comment
requirements, an agency’s final rule must be a logical
outgrowth of the version set forth in its notice of proposed
rulemaking. Covad Comms. Co. v. FCC, 450 F.3d 528, 548
(D.C. Cir. 2006). If it were otherwise, agencies could evade
their notice-and-comment obligations by adopting final rules
unrelated to their published proposals. An agency may not
leave the public to “divine [the agency’s] unspoken thoughts”
on a final rule “surprisingly distant from the proposed rule.”
CSX Transp., Inc. v. Surface Transp. Bd., 584 F.3d 1076, 1080
(D.C. Cir. 2009) (citing Int’l Union, United Mine Workers of
Am. v. Mine Safety & Health Admin., 407 F.3d 1250, 1259-60
(D.C. Cir. 2005) (formatting modified)). At the same time, the
APA does not require that rules be subjected to multiple cycles
of notice and comment until the version adopted as final is
identical to the last notice of proposed rulemaking; after all, the
very premise of agencies’ duty to solicit, consider, and respond
appropriately to comments is that rules evolve from conception
to completion. The public right to have a say in such
development is honored so long as affected parties “should
have anticipated” the final rule in light of the notice. Covad
Comms. Co., 450 F.3d at 548. Notice suffices when it has
 33
“expressly asked for comments on a particular issue or
otherwise made clear that the agency was contemplating a
particular change.” CSX Transp., 584 F.3d at 1081.

The change from barometric pressure to geometric altitude
in the Remote ID Rule was no surprise. The FAA proposed to
include the altitude of a drone’s control station as a Remote ID
message element to enable the agency to “locate an operator in
circumstances under which the person manipulating the flight
controls . . . is not at ground level, such as a person operating a
[drone] from the roof of a building.” Final Rule, 86 Fed. Reg.
at 4420. The Proposed Rule acknowledged that only one form
of altitude measurement was needed, and it favored using
barometric pressure. Proposed Rule, 84 Fed. Reg. at 72,473.
The FAA initially reasoned that barometric pressure is more
precise and is the standard way altitude is measured in aviation.
Final Rule, 86 Fed. Reg. at 4420. Nonetheless, the agency
requested comment on whether both barometric pressure and
geometric altitude measurements should be part of the Remote
ID message. Proposed Rule, 84 Fed. Reg. at 72,473.

After reviewing comments favoring geometric altitude’s
compatibility with existing drone technologies, the FAA
elected in the Final Rule to require only geometric altitude
measurement. “Many commenters recommended using
geometric altitude for control stations, suggesting that it would
be of greater usefulness, reliability, and less technically
complex to integrate into” unmanned aircraft systems. Final
Rule, 86 Fed. Reg. at 4420. Whereas drone control stations are
not ordinarily equipped with the barometric pressure sensors
used on airplanes, making compliance with that requirement
“difficult and costly,” most existing smart devices typically
used as control stations for recreational drones are equipped
with GPS that measures geometric altitude. Id. Barometric
pressure instruments also require more calibration, testing, and
 34
maintenance than GPS. Id. The Final Rule thus requires the
Remote ID signal to include the location of the drone and its
control-station or takeoff location using geometric instead of
barometric pressure altitude. See id. at 4422-23 (concerning
the drone’s altitude), 4431-32 (concerning the altitude of a
Broadcast Module drone’s takeoff location).

Brennan objects that the “FAA requested comment on
whether both geometric and barometric should be transmitted,”
thus giving “no indication” that GPS alone might be used, or
of the degree of accuracy the FAA would require of GPS
altitude measurements. Pet. Br. at 41 (formatting modified).
But it remains a mystery how requiring one altitude
measurement rather than both could be prejudicial. As for the
accuracy the FAA requires of GPS, the agency explained that
it was “adopting a geometric altitude accuracy requirement that
is compatible with the performance requirements being
established for cellular service providers under the E911
mandate that allows emergency service providers to accurately
locate the geographic position of the mobile device.” Final
Rule, 86 Fed. Reg. at 4431. In view of the FAA’s call for
comments on both barometric and geometric altitude, Brennan
had the requisite opportunity to comment on the achievable
accuracy of GPS—an opportunity taken up by other
commenters. See, e.g., Walter Bender, Remote ID NPRM
Comments at 1 (Mar. 3, 2020),
https://www.regulations.gov/comment/FAA-2019-1100-
50995 (analyzing and recommending accuracy requirements
for both barometric and GPS altitude measurements); Gregory
Walden, Comments of the Small UAV Coalition at 24-25 (Mar.
2, 2020), https://www.regulations.gov/comment/FAA-2019-
1100-50278 (same). At bottom, Brennan’s objection to
including accurate GPS location-identification information in
Remote ID messaging appears to be a variant of his Fourth
 35
Amendment privacy claim and fails for the reasons explained
above.

Brennan’s contention that the Proposed Rule gave no
notice of the radio broadcast module option in the Final Rule
also fails. Under the Rule, owners of drones incapable of
broadcasting the requisite Remote ID message who wish to fly
their drones outdoors outside of an FAA-recognized
identification area may do so by retrofitting their drones with
broadcast modules to meet the Rule’s Remote ID requirements.
Brennan insists that he lacked the chance to voice concerns that
a broadcast module would cause radio frequency interference
problems with certain types of equipment that would
negatively affect its use. But the FAA invited comment on the
viability of a broadcast module option. Proposed Rule, 84 Fed.
Reg. at 72,490. The call for comments stated that any retrofit
module would have to comply with Remote ID requirements,
which in the Proposed Rule included use of radio broadcasts or
internet transmissions. Members of the public had the
opportunity to voice their concerns that retrofitting certain
drones with radio broadcast modules could interfere with radio
signals used for navigation, video recording, or any other
specialized function.

Because the Final Rule was a logical outgrowth of the
Proposed Rule, Brennan had notice of and the opportunity to
comment on the features to which he now objects.

C. There was no consultation failure

Brennan contends that, despite Congress’s express
directive that it do so, the FAA somehow fell short of fulfilling
its statutory duty to consult on the Remote ID standards with
the President of the Radio Technical Commission for
Aeronautics, Inc. (RTCA) and the Director of the National
 36
Institute of Standards and Technology (NIST). FAA Extension
Act § 2202(a), 130 Stat. at 629. His complaint seems to be that
the “FAA’s ID Area requirement is not based on any standards
developed by or in coordination with the [stakeholder] group
as mandated by Congress.” Pet. Br. at 46. Brennan claims that
the FAA thereby failed to fulfill what he sees as “a statutory
prerequisite to its rulemaking authority” that requires us to
vacate the Rule. Pet. Reply Br. at 31.

The FAA involved the RTCA and NIST in its preparation
for and development of the Rule, just as Congress directed.
The RTCA is a nonprofit organization that provides technical
guidance on a range of aviation-related topics. See RTCA,
About us, https://www.rtca.org/about. NIST is an agency
within the Department of Commerce responsible for advancing
measurement science, standards, and technology in
coordination with government and industry. See NIST, About
NIST, https://www.nist.gov/about-nist. The 2016 enactment
Brennan invokes directed that:

The Administrator of the Federal Aviation
Administration, in consultation with the Secretary of
Transportation, the President of RTCA, Inc., and the
Director of the National Institute of Standards and
Technology, shall convene industry stakeholders to
facilitate the development of consensus standards for
remotely identifying operators and owners of
unmanned aircraft systems and associated unmanned
aircraft.

FAA Extension Act § 2202(a), 130 Stat. at 629. That
stakeholder convening was to consider remote identification
requirements, including appropriate requirements for
“different classifications of unmanned aircraft systems
operations, including public and civil,” and the feasibility of a
 37
publicly available database “of unmanned aircraft and the
operators thereof.” FAA Extension Act § 2202(b), 130 Stat. at
629. The FAA was to report to Congress within the year on
any standards developed, id. § 2202(c), 130 Stat. at 629, and to
proceed within the following year to promulgate regulations or
guidance implementing them, id. § 2202(d), 130 Stat. at 629.

The FAA duly consulted with the named entities,
convened its Unmanned Aircraft Systems Identification and
Tracking Aviation Rulemaking Committee comprised of
interested stakeholders, and issued a report to Congress
reflecting the requested recommendations. See FAA, ARC
RECOMMENDATIONS FINAL REPORT (2017), J.A. 561-773. The
RTCA served on the Committee, and NIST served as a
government observer to the Committee. See id. Appendix A at
2, J.A. 617; FAA Br. at 63 (citing Letter from the FAA to
Senator Roger Wicker, Chairman of U.S. Senate Committee on
Commerce, Science, and Transportation 1 (Feb. 13, 2019),
https://www.faa.gov/sites/faa.gov/files/2021-11/Letter-
Report-re-Sec.-2202-of-P.L.-114-190-2.13.19-Provided-to-
Congress_0.pdf); Pet. Reply Br. at 30 (acknowledging FAA-
Wicker letter).

Brennan complains that the Aviation Rulemaking
Committee “never considered or even mentioned the concept
of an ID Area” as an option for Remote ID compliance. Pet.
Br. at 46. But Congress did not require that the RTCA or NIST
weigh in on every facet of the proposed rule. See FAA
Extension Act § 2202(b), 130 Stat. at 629. Under the Final
Rule, a person may operate an unmanned aircraft lacking
remote identification capability only “at specific FAA-
recognized identification areas.” 86 Fed. Reg. at 4391.
Brennan would prefer homeowners and local parks to be able
to apply for ID Area status. See Pet. Br. at 58. But the FAA
received and considered many comments on that issue. See 86
 38
Fed. Reg. at 4414-17, 4437-38. The agency’s determination in
the Final Rule to limit eligibility to apply for ID-Area status to
community-based organizations and educational institutions is
not rendered invalid for want of evidence that the FAA
consulted the RTCA or NIST on that point.

D. The FAA adequately responded to significant
comments

Finally, Brennan accuses the agency of failing to heed
“significant critical comments” that, had they been addressed,
he says would “require a change in the rule.” Pet. Br. at 46.
He finds lacking the FAA’s explanation of the Rule’s legal
grounding and constitutional limits, its calculation of the
Rule’s regulatory costs, and its treatment of drone hobbyists’
interests.

The APA calls on us to determine whether an agency has
considered and responded adequately to major substantive
comments and, where it has failed to do so, remand for further
proceedings. 5 U.S.C. § 706(2)(A); see Sierra Club v. EPA,
863 F.3d 834, 838 (D.C. Cir. 2017) (citing Pub. Citizen, Inc. v.
FAA, 988 F.2d 186, 197 (D.C. Cir. 1993)). Our enforcement
of this and other APA procedural duties helps to ensure fair
treatment of people affected by agencies’ rules. “To this end
there must be an exchange of views, information, and criticism
between interested persons and the agency” in which all
significant factors are considered. Home Box Office, Inc., 567
F.2d at 35. But exhaustiveness itself is not the measure. The
agency must make clear the major policy issues at stake and
why it resolved them as it did. It need not respond to every
fact, idea, or opinion raised in comments, nor need it address
speculative or plainly baseless concerns. See id. at 35-36 &
n.58.
 39
Brennan argues that the FAA failed to address various
comments critical of the Proposed Rule. He says it overlooked
comments that the Rule exceeds the agency’s statutory
authority to regulate drone operations only within the
“navigable airspace” subject to FAA regulation, 49 U.S.C.
§ 40103(b), by instead purporting to apply throughout the
“airspace of the United States,” id. § 40103(a)(1), which he
views as more encompassing. He also says that the Rule
exceeds the scope of Congress’s power to legislate pursuant to
the Commerce Clause insofar as it applies to “the hobby of
model aviation.” Pet. Br. at 50. He asserts the FAA ignored
comments that its criteria for ID Areas run afoul of due process
(by restricting hobbyists’ access to public airspace) and the
First Amendment (by requiring as a condition of access to an
ID Area association with the organization sponsoring it). And
he accuses the FAA of sidestepping comments that the Rule
authorizes warrantless intrusions on homeowners’ privacy in
violation of the Fourth Amendment.

In both the Proposed Rule, 84 Fed. Reg. at 72,451, and
Final Rule, 86 Fed. Reg. at 4395, the FAA identified its
statutory authority. See 49 U.S.C. §§ 40103(b)(2), 44805. The
asserted constitutional concerns under the Commerce Clause,
the Due Process Clause, and the First Amendment are either
frivolous, or, like the Fourth Amendment concern, address
potential future applications rather than the facial validity of
the Rule itself, or both. The agency had no obligation to
respond to comments “incapable of affecting the final rule.”
City of Portland v. EPA, 507 F.3d 706, 715 (D.C. Cir. 2007).
And the FAA responded to Brennan’s Fourth Amendment
concerns. See 86 Fed. Reg. at 4435-36.

As for the FAA’s treatment of regulatory costs, Brennan
asserts the agency’s cost calculations were artificially low
because it failed to account for comments offering (1) higher
 40
estimates of the time and labor required to apply for FAA-
recognized ID Area designation and (2) higher aggregate drone
retrofit cost estimates by assuming slower replacement with
new Rule-compliant models. But the agency did address those
cost issues. See Final Rule, 86 Fed. Reg. at 4481, 4483; see
also FAA, REMOTE IDENTIFICATION OF UNMANNED AIRCRAFT
SYSTEMS NOTICE OF PROPOSED RULEMAKING – PRELIMINARY
REGULATORY IMPACT ANALYSIS 106-07 (Dec. 20, 2019), J.A.
337-38; FAA, REMOTE IDENTIFICATION OF UNMANNED
AIRCRAFT FINAL RULE – REGULATORY IMPACT ANALYSIS 114-
15 (Sept. 2020), J.A. 540-41. In any event, given that the
FAA’s total cost estimates range from $214 to $246 million,
Final Rule, 86 Fed. Reg. at 4489, the differences in the FAA’s
and Brennan’s estimates are slight; the adequacy of the FAA’s
response regarding what Brennan calculates as approximately
$1.4 million more in certain indirect compliance costs that he
asserts it should have considered is immaterial to the validity
of the Rule.

Finally, Brennan faults the FAA’s response to suggested
accommodations of drone hobbyists seeking more places to fly
and more freedom from the Rule’s requirements. He asserts
that the FAA “flat out did not respond” to the Academy of
Model Aeronautics’ comment that model aircraft should be
excepted from the Rule. Pet. Br. at 57. But the FAA did
acknowledge that suggestion; it excepted home-built drones
made for educational or recreational purposes from design and
production requirements, but not operational requirements.
See Final Rule, 86 Fed. Reg. at 4449.

The FAA also gave a reasoned response to comments
suggesting that homeowners and local governments be eligible
to establish ID Areas in backyards and local parks. The FAA
explained that it “intends most [unmanned aircraft systems] to
identify remotely,” and that operation without Remote ID at ID
 41
Areas “is primarily for those who are truly unable to use either
standard remote identification [drones] or remote identification
broadcast modules.” Id. at 4437. It defended the more limited
expansion allowing educational institutions and community-
based organizations to apply for ID Areas as “sufficient to meet
the needs of student model flyers” while avoiding further
expansion it feared could expand so far as to “undermine the
effectiveness of remote identification.” Id.

Brennan contends that the FAA did not adequately
respond to comments questioning the safety rationale for the
Rule—comments arguing that recreational drones have thus far
caused few documented harms, and that Remote ID
requirements have created rather than resolved safety risks to
drone pilots. The Rule reasonably describes the benefits of
Remote ID to mitigate a wide range of identified safety and
security concerns. See, e.g, Final Rule, 86 Fed. Reg. at 4391,
4394-97, 4418-20, 4490; see also Proposed Rule, 84 Fed. Reg.
at 72,454-55. Brennan acknowledges the agency’s response to
comments objecting that identification of drone pilots’ location
during flight can facilitate assaults against them and theft of
their equipment; his dissatisfaction with the substance of the
response relying on operator precautions and existing law and
law enforcement to address such attacks is no reason to
invalidate the Rule.

CONCLUSION

For all these reasons, we deny the petition for review.

So ordered.