Legal Research AI

Air Trans Assn Amer v. FAA

Court: Court of Appeals for the D.C. Circuit
Date filed: 2002-05-31
Citations: 291 F.3d 49
Copy Citations
26 Citing Cases

                  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-

__________
     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

__________
     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.

__________
     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 

__________
     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 

__________
     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 

__________
     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 

__________
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.