          United States Court of Appeals
                     For the First Circuit


No. 99-1888

        AVIATORS FOR SAFE AND FAIRER REGULATION, INC.,

                           Petitioner,

                               v.

                FEDERAL AVIATION ADMINISTRATION,

                           Respondent.


              ON PETITION FOR REVIEW OF AN ORDER OF

               THE FEDERAL AVIATION ADMINISTRATION


                             Before

                     Selya, Boudin and Lynch,

                         Circuit Judges.


     John M. Edwards with whom John C. Blessington and
Kirkpatrick & Lockhart LLP were on brief for petitioner.
     Charles W. Scarborough, Appellate Staff, Civil Division,
Department of Justice, with whom David W. Ogden, Acting
Assistant Attorney General, and Robert S. Greenspan, Appellate
Staff, Civil Division, Department of Justice, were on brief for
respondent.




                          July 25, 2000
              BOUDIN, Circuit Judge.      Petitioner, Aviators for Safe

and Fairer Regulation, Inc. ("Aviators"), is a trade association

of about fifty on-demand air charter companies.            It brings this

case to challenge a so-called notice of enforcement policy

issued   by    the   Federal   Aviation   Administration    ("FAA")   that

purports to interpret, and to express its intent to enforce, a

preexisting regulation governing how much rest pilots or other

flight crewmembers must get between flight assignments.

              Air charter companies furnish "air taxi" service to

customers on demand rather than on a scheduled basis.            The FAA

regulates such companies under Part 135 of its regulations, 14

C.F.R. pt. 135 (2000).         The regulation at issue in this case,

id. § 135.267(d), was adopted in its current form in October

1985 and aims to ensure that pilots have adequate rest for

purposes of air safety, see 49 U.S.C. §§ 40101(d), 44701(a)(4)-

(5) (1994 & Supp. II 1996).        It states, in relevant part, that

each flight assignment to unscheduled one- and two-pilot crews

"must provide for at least 10 consecutive hours of rest during

the 24-hour period that precedes the planned completion time of

the assignment."       14 C.F.R. § 135.267(d).

              The term "rest" is not defined in the regulation.         On

several occasions, the FAA sought to refine the term through




                                    -3-
rulemaking but those efforts were abortive.1           Then, on June 15,

1999, without prior notice or rulemaking proceedings, the FAA

issued a "notice of enforcement policy."         The notice said that

it was merely reiterating the FAA's "longstanding interpretation

of its regulations" concerning rest requirements and continued

in pertinent part:

          [T]he FAA has consistently interpreted the
          term rest to mean that a flight crewmember
          is free from actual work from the air
          carrier or from present responsibility for
          work should the occasion arise.    Thus the
          FAA previously has determined that a flight
          crewmember on reserve was not at rest if the
          flight    crewmember    had     a    present
          responsibility for work in that the flight
          crewmember had to be available for the
          carrier to notify of a flight assignment.

Notice of Enforcement Policy, 64 Fed. Reg. 32176, 32176 (1999).

The principal controversy centers upon how (and in one case

whether) the notice resolves two different scenarios, which we

shall   refer   to   as   the   duty-to-report   and    the   duty-to-be-

available.


    1See, e.g., Notice of Proposed Rulemaking, 60 Fed. Reg.
65951, 65959-61, 65976 (1995); Notice of New Task Assignment for
the Aviation Rulemaking Advisory Committee (ARAC), 63 Fed. Reg.
37167, 37167 (1998). The term "rest," again without definition,
is used in several other regulations establishing flight crew
rest requirements for larger and scheduled carriers, see 14
C.F.R. §§ 121.471(b), 135.265(b) (2000) (9 to 11 continuous
hours in the 24-hour period preceding completion of a flight
assignment); id. §§ 121.471(d), 135.265(d) (one uninterrupted
24-hour   period  weekly);   the  term   appears   to  be   used
interchangeably among these regulations.

                                   -4-
             In the duty-to-report scenario, a crewmember who is

nominally off duty has a responsibility during the period to

leave a contact number, to be fit to fly, to take any telephone

calls   or    other     communications      notifying     him      of    a   flight

assignment, and to report for that assignment in a reasonable

time (e.g., two hours).         In the duty-to-be-available scenario,

the same is true but the crewmember has the option to accept or

decline a flight assignment that is offered during this off-duty

period.      It is easy to see why such arrangements would be

attractive to an air taxi carrier.

             Under     either   scenario,    a   call   to    the       crewmember

followed     by   an   accepted   assignment      would      (at    some     stage)

terminate any "rest" that might otherwise be accruing.                         The

crewmember, to be eligible for the assignment, would have to

have met the "ten hours rest" quota based on "rest" that had

already occurred.        But the FAA's position in its notice as to

the duty-to-report scenario (the duty-to-be-available scenario

is a different issue) is that even if no call were made during

this nominal off-duty period, none of the period would count as

rest because the generic responsibility to leave a number, take

calls, and report if assigned would negate "rest" for the entire

period.




                                     -5-
             Aviators sought direct review of the notice under 49

U.S.C. § 46110 (1994), which permits any person "disclosing a

substantial interest in an order issued by" the FAA with respect

to aviation safety matters to seek review in an appropriate

court of appeals, id. § 46110(a).                  The court of appeals has

"exclusive jurisdiction to affirm, amend, modify or set aside

any part of the order and it may order" the FAA to conduct

further      proceedings.          Id.    §   46110(c).      We    consider    first

threshold issues as to our authority to review the notice; then,

Aviators' procedural claim that the notice required notice and

comment rulemaking; and last, Aviators' substantive attacks on

the FAA's position.

             1.   The FAA does not directly dispute that its notice

of enforcement policy constitutes an "order," but raises the

issue obliquely, saying that it is merely giving advance notice

of an intention to enforce the law.                    Whether a notice thus

limited would be reviewable is beside the point; here, the FAA's

"notice" adopts a firm interpretation of an existing regulation.

The   term     "order"    is       read    expansively    in      review   statutes

generally, 5 U.S.C. § 551(6) (1994) (an "order" includes "the

whole   or    a   part   of    a   final      disposition,     [including     those]

declaratory in form"), and this statute specifically, New York

v. FAA, 712 F.2d 806, 808 (2d Cir. 1983); Northwest Airlines,


                                           -6-
Inc. v. Goldschmidt, 645 F.2d 1309, 1313-14 (8th Cir. 1981).                         To

that extent, the notice here qualifies as a reviewable "order,"

assuming other conditions (e.g., finality, ripeness) are met.

            Several circuits (although not this one) have said that

there must be "an administrative record" for agency action to be

a reviewable order under section 46110.                      See, e.g., Green v.

Brantley, 981 F.2d 514, 519 (11th Cir. 1993); City of Alexandria

v. Helms, 728 F.2d 643, 646 (4th Cir. 1984).                      Yet almost all of

these    cases    find    that      the     requisite       record     need   not   be

substantial so long as the agency's position is definitive and

clearly expressed.       See San Diego Air Sports Ctr., Inc. v.                 FAA,

887 F.2d 966, 969 (9th Cir. 1989) (a letter may suffice).                            In

any event, an inadequate record is more likely to be a basis for

setting aside final agency action than for refusing to review

it.     See Citizens to Preserve Overton Park v. Volpe, 401 U.S.

402, 419-20 (1971).

            The FAA does not contest the notice's finality--and

with good reason.          The notice is unquestionably final in a

procedural    sense:          it    is    not    a   proposal     to   interpret      a

regulation, and there is no indication that the FAA plans to

conduct     further      proceedings            on   this    declaration.           See

Alexandria,      728   F.2d    at    646.        Rather,    the    FAA's   principal

challenge to our review at this time--its request that review be


                                          -7-
deferred until there is an actual enforcement proceeding in

which objections might be raised in defense--is an argument

properly considered under the rubric of ripeness.                     See Public

Serv. Comm'n v. Patch, 167 F.3d 15, 23 (1st Cir. 1998).

            An issue is ripe for judicial review if it is "fit" for

immediate review and delay would impose "undue hardship" on

litigants.     Abbott     Labs.   v.    Gardner,    387   U.S.   136,     148-49

(1967).    As to hardship, the FAA's notice promised "enforcement"

(after a 180-day grace period that has already expired, 64 Fed.

Reg. 32176, 32176 (1999)), not opportunities for negotiations or

further clarification, and enforcement may include penalties up

to   and   including    the   revocation     of    charters,     14    C.F.R.   §

13.19(b) (2000).       Conversely, compliance may also require major

changes in air taxi operations, and deferral of review would

clearly threaten hardship.         Cf. Lincoln House, Inc. v. Dupre,

903 F.2d 845, 847 (1st Cir. 1990).

            With respect to fitness, the most common concern is

whether a rule or order is framed in terms so general that only

its application to specific facts (usually in an enforcement

proceeding) would permit the court to make a reasoned judgment.

Patch, 167 F.3d at 23.        As to the duty-to-report scenario, we

think that the FAA's position is plain enough from the language




                                       -8-
of its notice,2 especially when read in light of prior statements

(discussed below), and involves a clear-cut pattern of conduct

that may arise frequently in air taxi operations.                In this

respect, the notice is well fit for review at this time.

          The     duty-to-be-available     scenario   is    different.

Although Aviators has presented a distinct pattern of conduct

likely to be important to air taxi operations, we find no

similar clarity in the notice (see note 2, below), or earlier

interpretive letters (see note 6, below), to show how the FAA

would resolve the scenario.      True, one footnote in the FAA's

brief, and its statements at oral argument, suggest that an

unrequited    duty-to-be-available    is   not   "rest,"   but   we   are

unwilling to bind the agency to the less-than-clear litigation

position of its lawyers in deciding whether a controversy is fit

for review.     Cf. Bowen v. Georgetown Univ. Hosp., 488 U.S. 204,

212-13 (1988).

          A final issue of "authority" which was not raised by

the FAA--indeed, it commendably conceded the point at oral

argument--deserves to be mentioned.         The review statute, 49



     2
     Pertinently, the FAA notice says that the crewmember must
be "free . . . from present responsibility for work should the
occasion arise."    64 Fed. Reg. 32176, 32176 (1999).        By
contrast, in the duty-to-be-available scenario, it is much less
clear that the crewmember has a "present responsibility for
work" since the assignment can be declined.

                                -9-
U.S.C.    §   46110    (1994),   imposes     a   sixty-day     time    limit    on

petitions for review unless "there are reasonable grounds for

not   filing    by    the   [sixtieth]   day"    after   the    order,    id.    §

46110(a).      Here, the petition for review (filed August 6, 1999)

is timely as to the notice of enforcement policy (issued June

15, 1999), but comes years after the order adopting the 1985

regulation at issue.          Yet, as we will see, Aviators could be

regarded in some respects as attacking the original regulation.

              If so, this case arguably falls within the proviso of

the   statute     permitting     a   later   challenge    where       there    are

"reasonable grounds" for the delay.3             Here, reasonable grounds

probably exist for a deferred attack inasmuch as neither the

original 1985 regulation nor accompanying commentary eliminated

uncertainty as to how the FAA might resolve any of a number of

scenarios (including the duty-to-report and the duty-to-be-

available) that might arise in practice.              Cf. Charter Township

of Huron v. Richards, 997 F.2d 1168, 1172-73 (6th Cir. 1993);

Greater Orlando Aviation Auth. v. FAA, 939 F.2d 954, 960 (11th

Cir. 1991).



      3
      The proviso is unusual (compare the Hobbs Act, 28 U.S.C. §§
2341-51 (1994 & Supp. II 1996)), but reviewing courts have often
read the Hobbs Act and like statutes as containing an implicit
"good cause" exception, see American Gas Ass'n v. FERC, 912 F.2d
1496, 1514 (D.C. Cir. 1990); RCA Global Comms., Inc. v. FCC, 758
F.2d 722, 730 (D.C. Cir. 1985).

                                      -10-
            2.     As the parties have briefed the issue, the first

question on the merits is procedural:                    whether the FAA was

required to conduct notice and comment rulemaking before issuing

its notice of enforcement policy.                If the FAA were altering or

enlarging    obligations      imposed       by   a    preexisting    regulation,

notice and comment rulemaking would be required, see Warder v.

Shalala, 149 F.3d 73, 80-81 (1st Cir. 1998), cert. denied, 67

U.S.L.W. 3470 (U.S. Apr. 19, 1999) (No. 98-1131), but a mere

"interpretation" can ordinarily be done without rulemaking, id.

at   80;    see    also   5   U.S.C.    §     553(b)(B)    (1994).        Whether

"ordinarily" means "always" is an interesting question.                         Cf.

Dugan v. Ramsay, 727 F.2d 192, 196-98 (1st Cir. 1984) (rejecting

agency "interpretation" without rulemaking); Jicarilla Apache

Tribe v. FERC, 578 F.2d 289, 292-93 (10th Cir. 1978) (same).

            To determine whether the FAA is altering or enlarging

the 1985 regulation depends on the "meaning" of the original

regulation (validity is a different question).                   See Warder, 149

F.3d at 80-81.      The 1985 regulation, as applied to the scenarios

at issue, supplies no very clear answer because it does not

define "rest" or otherwise indicate how the FAA would resolve

the duty-to-report scenario.            See 14 C.F.R. 135.267(d) (1986);

50   Fed.   Reg.    29306,    29311-14,       29317    (1985).      Nor   is   help

provided by a precursor regulation first codified in 1970 from


                                       -11-
which the key 1985 language was borrowed.           See 14 C.F.R. §

135.136(b) (1970); 34 Fed. Reg. 1443, 1444 (1969).

          Of course, subsequent administrative interpretation is

often treated as evidencing, or substituting for, a supposed

"original" intent.       See Mullins Coal Co. v. Director, 484 U.S.

135, 159-60 (1987).       And the gist of Aviators' claim is that

despite   the open-textured quality of the 1985 regulation, it

had been given meaning over time and had come to rest in a well-

settled interpretation that is favorable to Aviators' cause,

which the notice of enforcement policy mistakenly contradicts.

A less extreme version is that at least the agency must give

"reasons" why it is reversing an established position.             See

Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463

U.S. 29, 43 (1983); Citizens Awareness Network, Inc. v. Nuclear

Regulatory Comm'n, 59 F.3d 284, 290 (1st Cir. 1995).

           As to the duty-to-report scenario, it is clear to us

that   there   is   no   "reversal":    the   FAA   has   consistently

maintained--in its interpretive letters, bulletins, and other

statements--that an off-duty period encumbered by the threat of

interruption from a mandatory assignment is not rest.             For

example, Flight Standards Information Bulletin 92-02 (Jan. 24,

1992) states that "the FAA has consistently interpreted its

"nest" requirement to be satisfied only if the rest time is:


                                 -12-
determined prospectively . . . .           A period of time during which

a pilot has a present responsibility for work, if called, does

not qualify as a rest period.         This should be contrasted with a

pilot who does not have a present responsibility to fly, when

called."4

              Admittedly, this position, whether in its most recent

articulation        in   the   notice,     or   in   the   FAA's   previous

explanations, is not as clear as it could be;5 but it is clear

enough.       In fact, there are interpretative statements to the

same effect preceding 1985.         See, e.g., Letter from A.W. Lalle,

Acting Associate General Counsel, FAA, to John F. Nevins, Air

Line       Pilots   Association   (Feb.    5,   1968)   ("[W]hen   a   flight



       4
     See also Letter from Donald P. Byrne, Assistant Chief
Counsel, FAA, to Frederick G. Pappas, Jr., Director, Flight
Services, Midwest Corporate Aviation, Inc. (June 24, 1991) ("[A]
rest period must be prospective in nature. Stated another way,
a flight crewmember must be told in advance that he or she will
be on a rest period for the duration required by the
regulations.   In addition, a rest period must be free of all
restraint.   However, the Agency's interpretations hold that
receipt of one telephone call or beeper call does not constitute
a violation of a rest period provision.      Moreover, a flight
crewmember in a rest period must be free of present
responsibility for work should the occasion arise.").
       5
     Interestingly, "rest period" is defined in section
135.273(a), a different section of the same subpart as the
regulation at issue, added in 1994 to govern flight attendants
in air charter operations. 14 C.F.R. § 135.273(a) (2000); 59
Fed. Reg. 42663, 42663 (1994).    It is there defined as "the
period free of all responsibility for work or duty should the
occasion arise," the very language used in the 1999 notice.

                                    -13-
crewmember    is   required     by    the    air   carrier   to   hold   himself

available to call, it constitutes a restraint which interrupts

the 24-hour period, which we have held should be free from a

loss of freedom or restraint.").              More important, there is no

evidence that the FAA has ever said that the duty-to-report

scenario did count as rest.             The 1992 FAA bulletin on which

Aviators relies, which we have just quoted, actually hurts its

"reversal" claim.

            Nor are we troubled by Aviators' argument that the

FAA's   current      position    on    the    duty-to-report       scenario    is

inconsistent with a decision by the Eighth Circuit.                    See United

States v. Ozark Airlines, Inc., 506 F.2d 526 (8th Cir. 1974).

That decision construed a weekly rest requirement regulation, 14

C.F.R. 121.471(d) (1970), and inferred from the use of "duty" in

other subsections that rest "from all further duty" meant rest

from "duty aloft."       Ozark, 506 F.2d at 237.             "Duty aloft" was

changed to "flight time" in the 1985 version of this regulation

to   make    clear    that      "duty,"      for   purposes       of   the   rest

requirements, was a broader concept than "duty aloft."                    See 14.

C.F.R. §§ 121.471(a)-(c) (1986).

            By contrast, the FAA has been much less consistent as

to the duty-to-be-available scenario. The relevant interpretive




                                      -14-
letters appear not merely in tension, but at odds,6 and on this

point, the 1992 Bulletin is arguably helpful to Aviators.                     See

Flight Standards Information Bulletin 92-02 ("A period of time

during which a pilot has a present responsibility for work, if

called, does not qualify as a rest period.                     This should be

contrasted    with     a    pilot       who    does   not   have    a     present

responsibility    to       fly,   when    called.").        But,   as     earlier

explained, we still do not know for sure how the FAA would

resolve this latter scenario.            3.    This brings us to Aviators'

substantive attacks, whether treated as attacks on the notice or

on   the   regulation      itself.        Here,    the   FAA   starts     with   a

substantial   advantage:          the    question     how   much   rest    flight

crewmembers should be given to guard against pilot fatigue and

what interruptions should count against satisfying the ten-hour

rest requirement are technical issues involving safety where the

agency's latitude is substantial.                 See 49 U.S.C. § 40101(d),


     6Compare Letter from Donald P. Byrne, Assistant Chief
Counsel, FAA, to Frederick G. Pappas, Jr., Director, Flight
Services, Midwest Corporate Aviation, Inc. (June 24, 1991)
("Does a pager check during a 24 hour standby period interrupt
crew rest? . . . [S]tandy does not constitute crew rest. The
pager check does not interrupt crew rest because crew rest is
not taking place."), with Letter from Donald P. Byrne, Assistant
Chief Counsel, FAA, to B. Stephen Fortenberry, Evergreen
International Airlines, Inc., (undated, in response to a letter
dated October 12, 1989, with respect to section 121.471(d)) ("Is
telephone standby in a hotel or at home 'duty'? No, not in the
sense that it produces the need for the rest period required by
section 121.471(d).").

                                        -15-
44701(a)(4)-(5) (1994 & Supp. II 1996); see also Bargmann v.

Helms, 715 F.2d 638, 641-42 (D.C. Cir. 1983); Air Line Pilots

Ass'n Int'l v. Quesada, 276 F.2d 892, 898 (2d Cir. 1960).           And

absent a mistake of law, the standard of review is whether the

agency's   actions   are   arbitrary   or   capricious,    5   U.S.C.   §

706(2)(a) (1994), and whether any fact findings it made rest on

substantial evidence, 49 U.S.C. § 46110(c) (1994).

           Nevertheless, Aviators says that the FAA admits that

a brief, unexpected phone call from the carrier does not disturb

rest so as to require the ten-hour clock to be restarted.          See,

e.g., Letter from Donald P. Byrne, Assistant Chief Counsel, FAA,

to Albert C. Pod, Vice President, Executive Jet Management (Apr.

19, 1991).   The FAA verified at oral argument that it has not

disclaimed that position, and indeed, the language of the 1999

notice --"if the flight crewmember . . . had to be available for

the carrier to notify of a flight assignment"--arguably would

not be triggered by an unanticipated phone call.          Aviators says

that, in light of this concession, it is irrational to deny the

"rest" label in the duty-to-report scenario when no call in fact

occurs.

           We do not agree.    The agency is perfectly entitled to

regard a single unexpected phone call as less of a psychological

interruption to pilot rest than the continuing burden that


                                -16-
exists in the duty-to-report scenario even when no call occurs.

In the latter case, the pilot is effectively on a leash and

knows that at any point (after ten hours) he may be summoned

back to duty, for which he must remain "fit" to fly.                    Whether or

not   the    FAA    has   drawn    the    line    in    the   right    place,   the

distinction drawn is not irrational.

             Aviators' best claim is that there is no "explanation

or evidence" in the record that excluding the duty-to-report

time from "rest" is "necessary for, or even advances" safety.

And, although the FAA has elsewhere referred to "scientific

studies of fatigue," Notice of Proposed Rulemaking, 60 Fed. Reg.

65951,      65951   (1995),   it    points       to    no   evidence   or   even   a

thoughtful discussion of the specific issue either in the notice

or in the order adopting the 1985 regulation.                         Instead, the

FAA's brief offers an explanation.                To remove the taint of post

hoc rationalization, see State Farm, 463 U.S. at 50; Natural

Resources Defense Council v. EPA, 824 F.2d 1258, 1286 & n.19

(1st Cir. 1987), we note that the explanation is pretty obvious;

the harder question is whether it is sufficient.

             The FAA's commonsense explanation is this:                  given the

purpose of the rest requirement to assure that the flight crew

is refreshed and alert, anything that materially compromises a

state of affairs conducive to rest threatens refreshment and


                                         -17-
alertness; and a flight crewmember who is on call and subject to

the various duties imposed by the duty-to-report scenario is

less likely to be as refreshed and alert as one who need not

worry that a demand to fly may come at any time.                  This is

plausible enough; neither administrators nor judges are expected

to ignore the known realities of human existence.               See, e.g.,

Texas E. Prods. Pipeline Co. v. OSHA, 827 F.2d 46, 49 (7th Cir.

1987) (affirming agency's "common sense reading" that a "hole in

the ground is, after all, a hole in the ground").

           The force of this commonsense explanation is reinforced

by the fact of its long standing--at least fifty years.                 In

1949,    the   acting   general   counsel   of    the   Civil     Aviation

Administration was asked for an interpretation of then-existing

"relief from all duty" requirements.             Letter from Robert P.

Boyle, Acting General Counsel, Civil Aviation Administration, to

Coordinator, International Field Office, Lima, Peru (April 22,

1949).   The inquiry presented the following scenario:            "[An air

carrier] schedules a 'stand by' crew which must remain at home

subject to immediate call as replacement in case any of the

originally scheduled crew are unable, because of sickness, etc.,

to take the trip out as scheduled.       This 'stand by' crew, if not

called as a replacement on that day, is then scheduled as a

regular crew for a trip on the following day."          Id.


                                  -18-
          In response, the acting general counsel ruled:

          This appears to be such a lack of freedom of
          restraint and release from duty as to
          prevent the full and free exercise of an
          opportunity to rest intended by the rest
          period   provisions   of   the   Civil   Air
          Regulations.    It is immaterial that the
          pilots are not required to report to the
          airport or actively engage in work for the
          air carrier during the period of the stand
          by schedule. The term "relief from duty" as
          used in the above-noted section means that
          the pilot must be relieved from either
          actual work for the air carrier or present
          responsibility for such should the occasion
          arise.   A "stand by" schedule of the type
          described in the memorandum does not provide
          such relief from all duty with the air
          carrier.

Id.

          Of     course,   without    "evidence,"      we    have   no   way    of

knowing just how much these stand-by duties do compromise rest.

But   agencies     often   make   choices      where        no   evidence      can

demonstrate a single right answer.          Determining cut-off toxicity

exposures in environmental regulation, see Public Citizen Health

Research Group v.      Tyson, 796 F.2d 1479, 1504-05 (D.C. Cir.

1986), or rates of return in utility cases, see Borough of

Ellwood City v. FERC, 731 F.2d 959, 974-75 (D.C. Cir. 1984), are

good examples.     Where, as here, the agency’s choice appears to

be within a zone of reasonableness, a court will normally defer.

See Universal Camera Corp. v. NLRB, 340 U.S. 474, 477 (1951);



                                     -19-
Consolidated Oil & Gas, Inc. v. FERC, 806 F.2d 275, 279 (D.C.

Cir. 1986).

            The    more       serious       difficulty         is   the     lack    of    an

opportunity       for   Aviators       or    other       opponents     to    offer      such

rebuttal commentary or evidence.                   But, of course, Aviators has

not claimed to have medical studies or expert testimony to show

that the restrictive reading serves little or no purpose: it

says only that the FAA has failed to provide supporting evidence

of    its   own.         Perhaps       Aviators          can    develop         compelling

physiological evidence or collect the testimony of affected

pilots to show that duty-to-report time gives pilots as much

"rest" as time at home with no overhanging responsibilities.                              If

so, Aviators can file a petition tendering the evidence and

asking the FAA to modify its regulation accordingly.                              5 U.S.C.

§ 553(e) (1994).

            This    is    a    close    case       and    we    have      given    careful

consideration as to whether a remand might be warranted.                                 But

the   FAA’s   position        on   duty-to-report           time    is     on     its   face

plausible even without evidentiary support; this position has

been consistent over time, even assuming that enforcement has

been lax; and there is no indication from Aviators that it could

supply useful evidence if we did order a remand.                          The FAA should

not assume that the duty-to-be-available scenario--only a step


                                            -20-
further   down      the    road    but     a     significant       step   since    the

crewmember could refuse the assignment--would automatically be

sustainable on the same basis.

            A somewhat different rationale for its narrow view of

"rest" seems to be articulated in the FAA's brief in this court

which might, if adopted by the agency itself, provide additional

support for its position on the duty-to-report scenario and also

apply   equally     to     the    duty-to-be-available             scenario.       The

reasoning    does    not    depend        on   the    psychological       burden    of

overhanging      obligations        but    on     the        possible   threat    that

recalling the flight crewmember to duty after the initial ten

hours of rest could throw off the sleeping rhythms of pilots in

an unacceptable way.7            This concern, which the FAA itself may

never have articulated, may or may not be substantial, and we

express no opinion on the merits.

            Last,    Aviators       says       that     the     FAA's   position    is

unreasonable      and      unfair     because           no     corresponding      rest

requirements exist for fractional ownership programs, which



    7 The example given by the FAA brief (slightly corrected) is
of a pilot who goes off duty at midnight on Monday night, wakes
on Tuesday at 6:30 a.m. and would normally go to sleep again at
11 p.m. If the pilot is subject to recall on two hours' notice
after 10 a.m. on Tuesday, conceivably he could be called at 10
p.m. on Tuesday for a flight at 12:30 a.m. on Wednesday at which
point he will have been awake for 18 hours already, unaware that
sometime during that period he should have gotten some sleep.

                                          -21-
allegedly compete with air taxi carriers but are governed by

Part 91 of the FAA's regulations, 14 C.F.R. 91 (2000).          This

argument has not been well developed in this court; and there

may be substantive differences in operations that justify the

FAA's   decision   to   regulate   the   two   kinds   of   programs

differently.   But the FAA would have some explaining to do if

the two sets of operations are pertinently the same, especially

if there is a competitive relationship between them.        Cf. Town

of Norwood v. New England Power Co., 202 F.3d 392, 402-03 (1st

Cir.), petition for cert. filed, 68 U.S.L.W. 3756 (U.S. May 30,

2000) (No. 99-1914).

          However, agencies are not normally required to solve

all similar problems at one time.     See Mobil Oil Exploration v.

United Distrib. Co., 498 U.S. 211, 231 (1991).          The FAA is

currently reviewing its regulation of those fractional ownership

programs in separate proceedings.     Aviators is free to argue its

case in those proceedings, and if unsuccessful, it may seek

review of that agency action under the same statute that enabled

review in this case, 49 U.S.C. § 46110 (1994), or file a

petition for rulemaking to modify the current regulation         (14

C.F.R. § 135.267(d) (2000)) and spell out then the disparate

impact claim in greater detail, 5 U.S.C. § 553(e) (1994).




                               -22-
          Accordingly, we sustain the FAA as to the duty-to-

report scenario and treat as unripe Aviators' claims regarding

the duty-to-be-available scenario.       With respect to the latter,

Aviators is free to seek a formal declaratory ruling from the

FAA and to present its policy arguments and evidence to the

agency.   See 5 U.S.C. § 554(e) (1994).          While the agency has

discretion to refuse such a ruling, that refusal is reviewable

for abuse of discretion, see Intercity Transp. Co. v. United

States, 737 F.2d 103, 106-07 (D.C. Cir. 1984); cf. DeNovellis v.

Shalala, 124 F.3d 298, 313 (1st Cir. 1997), and we think that a

refusal   to   tell   Aviators   in   advance   whether   the   scenario

constitutes "rest" would itself require a lot of explaining.

          The petition for review is denied to the extent stated

and otherwise dismissed as presenting an issue unripe for review

at this time.

          It is so ordered.




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