United States Court of Appeals
FOR THE DISTRICT OF COLUMBIA CIRCUIT
Argued January 18, 2002 Decided May 31, 2002
No. 01-1027
Air Transport Association of America, Inc.,
Petitioner
v.
Federal Aviation Administration,
Respondent
Air Line Pilots Association, International, et al.,
Intervenors
No. 01-1303
Air Transport Association of America,
Petitioner
v.
Federal Aviation Administration,
Respondent
No. 01-1306
Regional Airline Association,
Petitioner
v.
Federal Aviation Administration,
Respondent
On Petitions for Review of an Order of the
Federal Aviation Administration
Michael S. Sundermeyer argued the cause for Air Trans-
port Association of America, Inc.
Lorraine B. Halloway argued the cause for Regional Air-
line Association. R. Bruce Keiner Jr. was on brief.
Edward Himmelfarb, Attorney, United States Department
of Justice, argued the cause for the Federal Aviation Admin-
istration. Robert S. Greenspan, Attorney, United States
Department of Justice, was on brief.
Joseph L. Manson III and Douglas W. Hall were on brief
for intervenor, Regional Aviation Partners.
Jonathan A. Cohen, James W. Johnson and Daniel M.
Katz were on brief for intervenors Air Line Pilots Associa-
tion, International and Coalition of Airline Pilots Associations.
Before: Edwards, Henderson and Garland, Circuit
Judges.
Opinion for the court filed by Circuit Judge Henderson.
Karen LeCraft Henderson, Circuit Judge: Air Transport
Association of America, Inc. (ATA) and Regional Airline
Association (RAA) seek review of the Federal Aviation Ad-
ministration's November 20, 2000 interpretation (issued by
letter) of Federal Aviation Regulation 121.471, 14 C.F.R.
s 121.471 (FAR 121.471), and attendant Notice of Enforce-
ment Policy (Notice) entitled "Flight Crewmember Flight
Time Limitations and Rest Requirements," published in the
Federal Register, 66 Fed. Reg. 27,548 (May 17, 2001). ATA
contends the letter interpretation and Notice are inconsistent
with the plain language of FAR 121.471. In addition, ATA
maintains that the letter interpretation constitutes a substan-
tive change to FAR 121.471 and, accordingly, requires notice-
and-comment rulemaking under the Administrative Proce-
dure Act (APA), 5 U.S.C. ss 551 et seq. We disagree.
I.
The Federal Aviation Act of 1958, 49 U.S.C. ss 40101 et
seq. (Act), directs the Administrator of the Federal Aviation
Administration (FAA) to "promote safe flight of civil aircraft
in air commerce" by prescribing "regulations in the interest
of safety for the maximum hours or periods of service of
aircrew and other employees of air carriers." 49 U.S.C.
s 44701(a)(4). The rules issued by the FAA under section
44701(a)(4) of the Act are generally referred to as "flight time
limitations."1 In 1985, pursuant to notice-and-comment rule-
making, the FAA promulgated FAR 121.471, establishing
flight time limitations and rest requirements for "flight crew-
members engaged in air transportation." See Flight Time
Limitations and Rest Requirements, 50 Fed. Reg. 29,306
(July 18, 1985). While the FAA was focused on simplifying
scheduling and giving air carriers added scheduling flexibility,
it also noted in the notice of proposed rulemaking that the
"current Part 121 rule ... provides no protection against
acute short-term fatigue for crewmembers." See Flight Time
Limitations and Rest Requirements for Flight Crewmem-
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1 The flight time limitation rules applicable to "major scheduled
air carriers" and "other airlines operating large transport category
airplanes" are contained in Part 121 of the FAR. The flight time
limitation rules applicable to scheduled air carriers operating air-
planes of 30 or fewer seats and air taxi operations are contained in
Part 135 of the FAR. The substance of the rules in Parts 121 and
135 is essentially the same and the rules are likewise interpreted.
bers, 49 Fed. Reg. 12,136, 12,136-7 (March 28, 1984). The
regulation allows a domestic airline "certificate holder" to
schedule, and a crewmember to accept, a flight assignment
only if the crewmember's total flight time does not exceed
yearly, monthly and weekly maximum flight time limitations.
14 C.F.R. s 121.471(a)(1)-(3). In addition, the regulation
establishes a maximum of eight hours of flight time between
"required rest periods." 14 C.F.R. s 121.471(a)(4). Pursuant
to subsection (b), during the twenty-four consecutive hours
preceding "the scheduled completion of any flight segment," a
crewmember must be scheduled for a rest period of at least
nine consecutive hours for eight hours or fewer of "scheduled
flight time"; ten consecutive hours of rest for more than eight
but fewer than nine hours of "scheduled flight time"; and
eleven hours of rest for nine or more hours of "scheduled
flight time." Id. s 121.471(b)(1)-(3). Subsection (c), however,
allows a carrier a measure of scheduling flexibility by way of
a "compensatory rest period." A required rest period of nine
hours may be "scheduled for or reduced to" a minimum of 8
hours if the crewmember is given compensatory rest of at
least ten hours "begin[ning] no later than 24 hours after the
commencement of the reduced rest period." Id.
s 121.471(c)(1).2 Compensatory rest, like required rest under
paragraph (b), may not be reduced or delayed under any
circumstances. See 14 C.F.R. s 121.471(e); see also 50 Fed.
Reg. at 29314 ("If a flight crewmember does not receive the
required number of hours of rest, the operator and the flight
crewmember are in violation of the regulation").3
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2 Subsection (c)(2) provides that required rest under (b)(2)--ten
hours for between eight and nine hours of scheduled flight time--
may be reduced to a minimum of eight hours if the crewmember is
given a compensatory rest of at least eleven hours and (c)(3)
provides that required rest under (b)(3) may be reduced to eight
hours if compensatory rest of at least twelve hours begins no later
than twenty-four hours after commencement of the reduced rest
period. See 14 C.F.R. s 121.471(c)(2) & (3).
3 While subsection (g) of FAR 121.471 provides that flight time
limits can be exceeded based on circumstances beyond the certifi-
cate holder's control (such as adverse weather conditions), it does
On September 26, 2000 Captain Richard D. Rubin, Chair-
man of the Flight Time--Duty Time Committee of the Allied
Pilots Association, submitted to the FAA several questions
regarding FAR 121.741, which questions apparently arose as
a result of changes in American Airlines's pilot reserve sys-
tem. On November 20, 2000 FAA Deputy Counsel James
Whitlow responded by letter (Whitlow Letter) to Rubin's
questions. The Whitlow Letter begins by stating that FAR
121.471(b)(1) requires a minimum of nine consecutive hours of
scheduled rest in the twenty-four hours preceding eight or
fewer hours of "scheduled flight time." The nine hours' rest
period may be reduced pursuant to FAR 121.471(c)(1) to a
minimum of eight hours if a minimum of ten hours of compen-
satory rest begins no later than twenty-four hours after the
commencement of the reduced rest period. More significant-
ly, the Whitlow Letter provides that "look-back" rest4 is
computed by using "actual expected flight time and taxi-in
time, based on the specific conditions that exist on the day, to
determine the scheduled arrival time for purposes of deter-
mining whether a flight should be commenced." Whitlow
Letter at 3. Irrespective of the carrier's published flight
time, then, "scheduled flight time" under FAR 121.471 should
be calculated (or recalculated) using the actual conditions on
the day of departure regardless whether the length of the
flight is longer or shorter than the originally scheduled flight
time. Once this information is calculated, "[i]f it is known, or
__________
not apply to the specified rest requirements which allow only the
scheduling flexibility spelled out in section 121.471(c). 14 C.F.R.
s 121.471(g).
4 The FAA defined "look-back rest" in an earlier rulemaking,
noting that "the rest requirement is based on the number of flight
hours looking back 24 hours from the completion of each flight
segment. If a pilot is scheduled for 4 hours of flight time late on
the first day and receives a reduced rest of 8 hours, he or she can
only be scheduled for up to 5 hours of flight time the following
morning, since the flight crewmember cannot be scheduled for 9 or
more flight time hours in 24 consecutive hours, based on an 8 hour
reduced rest period." Flight Time Limitations and Rest Require-
ments, 50 Fed. Reg. at 29,313.
reasonably should be known, that a flight segment will result
in less than eight hours of look-back rest for a particular
crew, the flight may not leave the gate." Whitlow Letter at
4.5
On January 18, 2001 ATA petitioned for review of the
Whitlow Letter (No. 01-1027) and RAA intervened. Four
months later, the FAA published in the Federal Register note
of its intent to "rigorously enforce existing regulations gov-
erning flight crewmember rest requirements." Notice, 66
Fed. Reg. at 27,548 (May 17, 2001). The Notice incorporated
the Whitlow Letter and advised that, within six months of the
date of the Notice's publication, the FAA intended to begin a
comprehensive review of flight scheduling practices and to
"deal stringently with any violations." Id. ATA and RAA
then filed separate petitions for review of the Notice (Nos.
01-1303 and 01-1306). We consolidated for review all three
petitions. See July 25, 2001 Consolidation Order.6 On Sep-
tember 5, 2001 we granted ATA's motion to stay the Notice.
II.
A. FAA's Interpretation of FAR 121.471
Because the Whitlow Letter7 constitutes the FAA's inter-
pretation of its own regulation, that interpretation must be
afforded substantial deference and upheld unless "plainly
erroneous or inconsistent with the regulation." Thomas Jef-
ferson Univ. v. Shalala, 512 U.S. 504, 512 (1994); see also
__________
5 If the flight is away from the gate but not yet in the air, the
flight may not take off. As a matter of enforcement policy, the
FAA will not charge a violation of the rest requirements if a delay
that first becomes known after the flight is in the air disrupts the
scheduled flight time, provided the required minimum reduced rest
and the compensatory rest occur at the completion of that flight
segment. See Whitlow Letter at 4.
6 Petitioners ATA and RAA are hereinafter referred to collective-
ly as ATA.
7 The "Whitlow Letter" hereinafter refers to both the Letter and
the Notice.
Paralyzed Veterans of America v. D.C. Arena L.P., 117 F.3d
579, 584 (D.C. Cir. 1997), cert. denied, 523 U.S. 1003 (1998).
Accordingly, we defer to the FAA's view unless "an alterna-
tive reading is compelled by the regulation's plain language or
by other indications of the [agency's] intent at the time of the
regulation's promulgation." Thomas Jefferson Univ., 512
U.S. at 512 (quoting Gardebring v. Jenkins, 485 U.S. 415, 430
(1988)). ATA contends that the Whitlow Letter, by requiring
the recalculation of a previously computed rest period, is
inconsistent with both the text and the purpose of FAR
121.471. ATA maintains that the phrase "scheduled comple-
tion of any flight segment" in subsection (b) means that
compliance with FAR 121.471 turns solely on the legality of
the originally established flight schedule irrespective of any
unexpected flight delay that may require re-scheduling. See
ATA Blue Br. at 25. The phrase, ATA asserts, cannot be
squared with the Whitlow Letter, which requires scheduled
flight time to take into account "actual expected flight time."
See Whitlow Letter at 4.
The FAA responds that the phrase "scheduled completion
of any flight segment" can reasonably be understood to
include a re-scheduled flight time based on actual flight
conditions. To be sure, "scheduled completion" can be con-
strued narrowly to refer only to the originally scheduled
flight completion time. The point, however, is that the FAA's
more expansive interpretation is not unreasonable. A re-
scheduled completion of a flight segment based on flight
conditions existing in fact is nonetheless a "scheduled" com-
pletion. Nothing in the text of FAR 121.471 or in the
ordinary usage of the word "scheduled"8 dictates that the
timetable of a particular flight segment can be determined
only when the schedule is originally created regardless of
adjustments made necessary by then-current conditions.
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8 One definition of "schedule" is a "procedural plan that indicates
the time and sequence of each operation." Webster's Ninth New
Collegiate Dictionary 1050 (1990). Completion of a flight segment
that allows for elapsing flight conditions is a "scheduled" completion
within that definition.
ATA's interpretations of subsection (b)'s term "scheduled
rest period" and subsection (c)'s reference to "reduce a
scheduled rest" are similarly unavailing. Its construction of
"scheduled rest" would allow a carrier to set up adequate rest
periods in advance and then disregard whether the rest
periods in fact occurred in light of actual flight conditions
because, under its construction, "scheduled rest" means "rest
[that] is lawfully established at the time of scheduling." ATA
Blue Br. at 26. ATA argues that the term refers only to a
future rest period and cannot justify a retrospective recalcu-
lation of rest a crewmember has already taken. Even if the
semantic point were valid, which we doubt as set forth below,
this argument ignores the structure of the regulation itself.
Under FAR 121.471, all rest requirements flow from the
"scheduled completion" of a particular flight segment. The
minimum rest requirements described in subsection (b) are
all keyed to the twenty-four hour period before the comple-
tion is to occur. The required rest must be scheduled during
those 24 hours. The carrier's first step therefore must be to
determine this scheduled completion time. It must then be
able to look back from that point to find a sufficient rest
period scheduled within the previous twenty-four hours.
Once that hour is allowed to change in response to unantic-
ipated delays, what is then recalculated is not (as ATA claims)
the rest that a crewmember has already received but instead
the 24-hour period in which the requisite amount of sched-
uled rest must occur. Moreover, ATA's prospective-only view
of "scheduled" is inconsistent with the ordinary meaning of
the word; a rest period already calculated, then recalculated,
can yet be understood as "scheduled" because it has been
"place[d] on a schedule." See Webster's Third New Interna-
tional Dictionary Unabridged 2028 (1993) ("schedule: vt-ed"
means "to place [o]n a schedule"). Nor does subsection (c), in
allowing a carrier to "reduce a scheduled rest," mean that a
rest period already completed cannot be recalculated in light
of actual flight times.
Further, the Whitlow Letter is not inconsistent with the
purpose of the 1985 amendment to FAR 121.471. Granted
that simplified scheduling and added scheduling flexibility for
carriers were two goals of the 1985 amendment, it does not
necessarily follow that an interpretation cabining a carrier's
flexibility is therefore unauthorized. The Whitlow Letter,
while imposing a measure of rigidity, nonetheless maintains
the system of flexible scheduling created by the amendment.
Moreover, "protection against acute short-term fatigue" of
crewmembers was also one of the FAA's goals. Flight Time
Limitations Rest Requirements for Flight Crewmembers, 49
Fed. Reg. at 12,137. The rest requirement regulation was
expressly promulgated under FAA's statutory authority to
issue "reasonable rules and regulations governing, in the
interest of safety, the maximum hours or periods of service of
aircrew and other employees of air carriers." Id. at 12,136
(citing statutory requirements codified at 49 U.S.C.
s 44701(a)(4)). While the 1985 amendment may have been
aimed at increasing scheduling flexibility, the FAA is statuto-
rily obligated to strike the best balance between flexibility
and safety. Having concluded the FAA's interpretation via
the Whitlow Letter represents a permissible construction of
FAR 121.471, we do not believe the fact that it may lessen
flexibility renders it invalid.
B. APA Issues
The FAA issued the Whitlow Letter without formal notice
and comment procedures. In so doing, ATA claims, the FAA
violated the APA because the Whitlow Letter (1) is a substan-
tive, not an interpretative, rule and (2) materially changes the
FAA's earlier interpretations of the required rest regulation.
We disagree. The interpretation contained in the Whitlow
Letter is "fairly encompassed" within the regulation it pur-
ports to construe and, therefore, under our circuit precedent
is an interpretative rule exempt from notice-and-comment
rulemaking. Moreover, none of the FAA's earlier interpreta-
tions of FAR 121.471 addresses precisely the issues ad-
dressed in the Whitlow Letter. Accordingly, the Whitlow
Letter does not mark a departure from the past.
1. Substantive vs. Interpretative Rule
The APA requires federal agencies to publish "[g]eneral
notice of proposed rulemaking" in the Federal Register, 5
U.S.C. s 553(b), and "give interested persons an opportunity
to participate in the rule making through submission of
written data, views, or arguments," 5 U.S.C. 553(c). Section
553, however, exempts "interpretative rules" and "general
statements of policy" from notice and comment procedures.
5 U.S.C. s 553(b)(3)(A). Nonetheless, it is well established
that an agency may not label a substantive change to a rule
an interpretation simply to avoid the notice and comment
requirements. See Appalachian Power Co. v. EPA, 208 F.3d
1015, 1024 (D.C. Cir. 2000).
The distinction between a substantive rule and an interpre-
tive rule can be less than clear-cut. See Syncor Int'l Corp. v.
Shalala, 127 F.3d 90, 93-94 (D.C. Cir. 1997) (listing cases);
General Motors Corp. v. Ruckelshaus, 742 F.2d 1561, 1565
(D.C. Cir. 1984) (en banc) (describing distinction as "en-
shrouded in considerable smog") (citation omitted). One
factor we consider in distinguishing between the two is
"whether the interpretation itself carries the force and effect
of law, ... or rather whether it spells out a duty fairly
encompassed within the regulation that the interpretation
purports to construe." Paralyzed Veterans, 117 F.3d at 588
(internal citation omitted) (emphasis added). The Whitlow
Letter's interpretation of FAR 121.471, we believe, is "fairly
encompassed" within the required rest regulation and is,
therefore, exempt from notice-and-comment rulemaking.
The FAA reasonably interpreted the required rest regulation
itself to require a carrier to recalculate past rest periods in
light of actual flight times, including those scheduled flight
times required to be rescheduled by existing flight conditions.
We cannot say that "in the absence of the [Whitlow Letter]
there would not be an adequate legislative basis to ... ensure
the performance of duties." American Mining Congress v.
Mine Safety & Health Admin., 995 F.2d 1106, 1112 (D.C. Cir.
1993). The provisions of FAR 121.471 incorporate both the
statutory requirement that the FAA establish flight time
limitations and required rest regulations "in the interest of
safety" and the phrase "scheduled completion of any flight
segment," which is reasonably understood to include a com-
pletion re-scheduled because of actual flight conditions. FAR
121.471 itself, then, provides the FAA with sufficient authori-
ty to impose the recalculation duty. The Whitlow Letter does
not impose "new rights or duties," Orengo Caraballo v. Reich,
11 F.3d 186, 195 (D.C. Cir. 1993), and therefore does not
require notice-and-comment rulemaking.9
2. Relation to Prior Agency Interpretations
Even if the Whitlow Letter is an interpretative rule, ATA
further contends, notice-and-comment rulemaking is nonethe-
less required because the Letter is inconsistent with earlier
FAA interpretations of FAR 121.471. "Rulemaking," as de-
fined in the APA, includes not only the agency's formulation,
but also its modification, of a rule. See 5 U.S.C. s 551(5)
("rule making" includes "agency process for formulating,
amending, or repealing a rule"); see also Paralyzed Veterans,
117 F.3d at 586 ("Under the APA, agencies are obligated to
engage in notice and comment before formulating regulations,
which applies as well to 'repeals' or 'amendments.' " (empha-
sis in original)). As the United States Supreme Court has
noted, APA rulemaking is required if an interpretation
"adopt[s] a new position inconsistent with ... existing regula-
tions." Shalala v. Guerney Mem'l Hosp., 514 U.S. 87, 100
(1995). In Alaska Prof'l Hunters Ass'n v. FAA, 177 F.3d
1030 (D.C. Cir. 1999), we held that "[w]hen an agency has
given its regulation a definitive interpretation, and later
significantly revises that interpretation, the agency has in
effect amended its rule, which requires notice and comment."
Id. at 1034 (citation omitted) (emphasis added); see also
Paralyzed Veterans, 117 F.3d at 586 (agency violates APA if
it makes a "fundamental change in its interpretation of a
substantive regulation without notice and comment"). In
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9 Although American Mining Congress identifies four factors,
any one of which demarks a legislative (as opposed to interpreta-
tive) rule, we apply both the first and fourth factors together to the
Whitlow Letter. Because the Whitlow Letter was not published in
the Code of Federal Regulations, nor did the FAA "explicitly
invoke[ ] its general legislative authority," the second and third
factors are inapplicable. American Mining Congress, 995 F.2d at
1112.
Alaska Hunters, Alaskan guides who transport their custom-
ers to hunting and fishing sites by airplane challenged the
FAA's requirement (imposed via a Notice to Operators) that
they comply with FAA regulations applicable to commercial
pilots. Id. at 1033. The Notice, promulgated without notice
and comment, reversed the FAA's thirty-year interpretation
that had exempted the guides. Id. The longstanding advice,
we held, had become "an authoritative departmental interpre-
tation, an administrative common law applicable to Alaskan
guide pilots"; hence, the Notice changing that interpretation
had to comply with notice-and-comment rulemaking. Id. at
1035.
ATA claims the Whitlow Letter changed "fifteen years of
[i]nterpretations" because "recalculation of past rest periods
[h]as never [been] required, even though the opportunity to
impose such a mandate was presented." Reply Br. at 17. Of
the prior interpretations ATA relies on, only one merits
discussion. Interpretation 1992-24, like the Whitlow Letter,
represents the FAA's response to a request for an interpreta-
tion of FAR 121.471. The request asked if a flight delay not
caused by the air carrier meant that "looking back 24 hours
from the actual completion time of the last flight, you will not
be able to find the applicable rest period required under FAR
121.471(b) and (c)." Interpretation 1992-24 at I-235 (JA
252). Pointing to the prospective language in FAR 121.471,10
the FAA declared that "deviations encountered in the opera-
tion of an otherwise legitimately scheduled flight are permit-
ted" so long as the schedule otherwise met the flight time
limitations and rest requirements. Id. Interpretation 1992-24
did not, according to ATA, "require recalculation of past rest
based on actual expected arrival time, [nor] ... mandate that
a normal, completed paragraph-(b) rest be turned, after the
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10 Under the scheduling provisions of FAR 121.471(a) and (b), no
air carrier "may" schedule a flight crewmember and no flight
crewmember "may" accept an assignment in excess of the specified
flight time limitations and rest requirements. See Interpretation
1992-24; see also Interpretation 1989-16 ("The key language of the
regulation is, '... may schedule ...,' ' ... may accept ...,' and '...
scheduled completion of any flight ...,' all of which are prospective
in application.").
fact, into a paragraph-(c) reduced rest." Reply Br. at 22.
The FAA insists that Interpretation 1992-24 speaks only to a
short delay that would still allow a carrier to give crewmem-
bers compensatory rest immediately following the extended
flight, relying on the following caveat contained in Interpreta-
tion 1992-24: "It is important to note[,] however, that the
delay cannot infringe on the next required rest period." In
the FAA's view, then, Interpretation 1992-24 addresses only
an alteration in the scheduled flight time short enough to
nonetheless provide for compensatory rest following the re-
duced rest in accordance with subsection (c). In contrast, the
Whitlow Letter addresses a delay that makes compliance with
either subsection (b) or (c) impossible in light of actual flight
conditions. Although Interpretation 1992-24 was not ex-
pressly limited to short delays, it nevertheless does not
provide a "definitive" interpretation inconsistent with that of
the Whitlow Letter. The FAA did not define the phrase
"operation of an otherwise legitimately scheduled flight" in
Interpretation 1992-24; if "operation" refers only to the in-
flight segment of a flight schedule, Interpretation 1992-24 is
simply a restatement of the FAA's longstanding enforcement
policy not to charge a rest violation for a delay that occurs
after takeoff. See also Interpretation 1998-7 at I-207. Be-
cause Interpretation 1992-24 can reasonably be interpreted in
this way,11 we do not believe the Whitlow Letter "significantly
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11 In Interpretation 1992-94, the FAA suggested that "The
regulation restricts an air carrier's scheduling of a pilot and a pilot's
accepting an assignment at the time of scheduling." (Emphasis in
original). In saying this, however, the agency in no way purported
to limit the definition of time of scheduling to time of original
scheduling. The Whitlow Letter can be seen as supplementing the
earlier interpretation by more precisely construing the term to
refer to scheduling that occurs any time before the flight in
question departs. Nor does the fact that the FAA previously
referred to the regulation as "prospective in application" suggest
any inconsistency with the Whitlow Letter. Even as we construe it,
the regulation applies prospectively from the time of scheduling;
the Whitlow Letter declares that the "scheduling" can be done up to
departure. While Interpretation 1992-94 may not have specifically
adopted this construction of scheduling, it in no way rejected it.
revises" a previous "definitive interpretation" of FAR 121.471.
See Alaska Hunters, 177 F.3d at 1034.
Other prior interpretations of FAR 121.471 buttress our
conclusion that the Whitlow Letter, in clarifying a carrier's
duty to recalculate previously computed rest periods based on
actual flight schedules, addresses only a theretofore unre-
solved aspect of the rest requirement. In a letter dated July
22, 1994 the FAA construed FAR 121.471 to require that a
"rest period must occur '... during the 24 hours preceding
the scheduled completion of any flight segment' " rather than
following the flight segment. See Interpretation dated July
22, 1994 (emphasis in original) (quoting FAR 121.471(b)).
While ATA is correct that the July 22, 1994 letter does not
specifically require recalculation of a rest period caused by an
unforeseen delay, it does nonetheless indicate that the FAA,
in 1994, required a carrier to provide a compensatory rest
period of ten hours at the end of day one despite the fact that
the crewmembers had received an extended rest period (more
than 24 hours) preceding the scheduled completion of flight
segment. More significantly, in Interpretation 1998-7, the
FAA declared that both the carrier and its crewmembers
would violate FAR 121.471 if they knew "prior to departure"
that due to a ground hold for weather the "scheduled arrival
time of the last flight segment would force the crew to begin
its compensatory rest period later than 24 hours after the
commencement of the reduced rest period." Interpretation
1998-7. The FAA's conclusion was based on the "actual
expected arrival time" calculated prior to departure and is
therefore consistent with its approach in the Whitlow Letter.
No prior FAA interpretation of FAR 121.471 approaches
the definitive interpretation that mandated notice-and-
comment rulemaking in Alaska Hunters. No prior interpre-
tation reflects an "administrative common law" that FAR
121.471 prohibits recalculation of past rest periods based on
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Interpretation 1992-94 is best understood as an ambiguous state-
ment whose details the Whitlow Letter has now filled in. Because
there is no discontinuity between the two, notice and comment were
not required.
"actual expected flight time." Alaska Hunters, 177 F.3d at
1035; see also Hudson v. FAA, 192 F.3d 1031, 1036 (D.C. Cir.
1999) (FAA interpretation did not require notice and com-
ment because it was simply "application of the regulation to a
changed situation which calls for a different policy"). Accord-
ingly, the Whitlow Letter does not alter a definitive prior
FAA interpretation of FAR 121.471.
For the foregoing reasons, the consolidated petitions for
review are denied.
So ordered.