 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued March 17, 2017               Decided August 29, 2017

                        No. 15-1158

                CITY OF PHOENIX, ARIZONA,
                        PETITIONER

                              v.

        MICHAEL P. HUERTA AND FEDERAL AVIATION
                    ADMINISTRATION,
                     RESPONDENTS


                 Consolidated with 15-1247


           On Petitions for Review of a Decision
           by the Federal Aviation Administration


    John E. Putnam argued the cause for petitioner City of
Phoenix, Arizona. With him on the briefs was Peter J. Kirsch.

     Matthew G. Adams, pro hac vice, argued the cause for
petitioners Story Preservation Association, et al. With him on
the briefs was Peter L. Gray.

     Lane N. McFadden, Attorney, U.S. Department of Justice,
argued the cause for respondents. With him on the brief was
John C. Cruden, Assistant Attorney General at the time the
brief was filed.
                               2

   Before: ROGERS and GRIFFITH, Circuit Judges, and
SENTELLE, Senior Circuit Judge.

    Opinion for the Court filed by Circuit Judge GRIFFITH.

   Dissenting opinion filed by Senior Circuit Judge
SENTELLE.

     GRIFFITH, Circuit Judge: In September 2014, the Federal
Aviation Administration changed longstanding flight routes in
and out of Phoenix Sky Harbor International Airport. The city
of Phoenix and a historic neighborhood association both
petitioned for review, alleging that the FAA’s action was
arbitrary and capricious. We agree.

                                I

     Phoenix Sky Harbor International Airport is one of the
nation’s busiest airports. To minimize the impact of the sound
of aircraft on residents, the FAA historically has routed flights
over industrial and agricultural parts of the City, and the City
has used zoning to minimize impact on residential areas and
either purchased or furnished with sound insulation the homes
most affected by flight paths, at a cost of hundreds of millions
of dollars.

     In response to a mandate from Congress to modernize the
nation’s air-traffic control system, see FAA Modernization and
Reform Act of 2012, Pub. L. No. 112-95,
§§ 101(a), 213(a)(1)(A), 126 Stat. 11, 47, the FAA sought to
alter the flight routes in and out of Sky Harbor and to employ
satellite technology to guide planes. For consultation on its
developing plans, the FAA formed the Phoenix Airspace Users
Work Group with the City and others.
                                 3

     One of the new flight paths the FAA devised would route
planes over a major avenue and various public parks and
historic neighborhoods. The new route would increase air
traffic over these areas by 300%, with 85% of the increase
coming from jets. The FAA consulted on the environmental
impact of this and other proposed changes primarily with a
low-level employee in Phoenix’s Aviation Department, who
warned the FAA that he lacked the expertise and authority to
discuss environmental matters on the City’s behalf. The FAA
never conveyed the proposed route changes to senior officials
in the City’s Aviation Department, local officials responsible
for affected parks or historic districts, or elected city officials.

     As plans progressed, the FAA used computer software to
model the noise impact of the proposed route changes. This
modeling predicted that two areas in Phoenix, which included
twenty-five historic properties and nineteen public parks,
would experience an increase in noise large enough to be
“potentially controversial.” But the agency concluded that
these projected noise levels would not have a “[s]ignificant
[environmental] impact” under FAA criteria. Joint Appendix
333, 334. Based on this conclusion, the FAA issued a
declaration categorically excluding the new flight routes from
further environmental review. The FAA shared these
conclusions with the State Historic Preservation Officer,
predicting that the new noise levels would not disrupt
conversation at a distance of three feet and would be no louder
than the background noise of a commercial area. The State
Officer concurred in this prediction.

    The FAA presented the finalized flight routes in an April
2013 meeting attended by a low-level project manager of the
City’s Aviation Department. The agency also sent the proposed
routes and maps showing affected areas to the other low-level
                               4
Aviation Department employee, with the caveat that plans were
“subject to change.” J.A. 302. In May 2014, the FAA notified
the Phoenix Airspace Users Work Group that the new routes
would take effect in September. The FAA did not share its
environmental conclusions with Airport management until the
day before the routes were to go into effect. Management asked
the FAA to delay implementation so the public could be
informed. The FAA refused.

    On September 18, 2014, the FAA published the new
routes, and related procedures, and made them effective
immediately. The public’s reaction was swift and severe: the
planes supplied the sound, the public provided the fury. In the
next two weeks, the Airport received more noise complaints
than it had received in all of the previous year. 1 Residents
complained that the flights overhead were too loud and
frequent and rattled windows and doors in their homes. Some
claimed that they had trouble sleeping uninterrupted, carrying
on conversations outdoors, or feeling comfortable indoors
without earmuffs to mute the noise.2

    In response to the uproar, the FAA held a public meeting
the next month that drew 400 attendees and hundreds of
comments. 3 There the agency promised to review the noise

    1
         See Brittany Hargrave, Phoenix Neighbors Protest Sky
Harbor Flight-Path Change, THE ARIZONA REPUBLIC, Sept. 30,
2014 (updated Oct. 1, 2014), http://azc.cc/YQlwu5.
     2
       See Ashley Thompson, Neighbors Upset at FAA’s New Flight
Patterns Hold Day of Protest, KNXV, Oct. 24, 2015,
http://www.abc15.com/news/region-phoenix-metro/central-
phoenix/neighbors-upset-at-faas-new-flight-patterns-hold-day-of-
protest.
     3
        See Miriam Wasser, Sound and Fury: Frustrated Phoenix
Residents Are Roaring Ever Since the FAA Changed Sky Harbor
Flight Paths, PHOENIX NEW TIMES, Mar. 4, 2015,
                               5
issue and update the City’s Aviation Department. The FAA
later claimed to have identified and corrected the problem:
aircraft had been straying from the new routes. The agency said
it was “teaming with the airport staff and industry experts” to
see what more could be done about the noise levels. J.A. 609.
But despite the FAA’s assurances, the City continued to receive
record numbers of noise complaints. In early December, the
City told the FAA that public concern remained high.

     That month the State Historic Preservation Officer also
asked the FAA to reconsider the new routes in light of their
impact on historic properties, which he said was far worse than
he had been led to believe. He said he had originally concurred
with the agency’s optimistic projections only out of deference
to the FAA’s technical expertise.

    Around the same time, the FAA’s Regional Administrator
met with Phoenix’s City Council and publicly admitted, “I
think it’s clear that . . . [our pre-implementation procedures
were] probably not enough because we didn’t anticipate this
being as significant an impact as it has been, so I’m certainly
not here to tell you that we’ve done everything right and
everything we should have done.” J.A. 773.

     A week after this concession, the City asked the agency to
reopen consultation and restore the old routes until the City and
the agency could engage the public in discussions. In response,
the FAA said it would work with the airport and airlines to
investigate additional changes to the flight paths. To that end,
the FAA promised to reconvene the original Working Group,

http://www.phoenixnewtimes.com/news/sound-and-fury-frustrated-
phoenix-residents-are-roaring-ever-since-the-faa-changed-sky-
harbor-flight-paths-6654056; Caitlin McGlade, FAA Will Study
Solution to Flight-Path Noise, THE ARIZONA REPUBLIC, Oct. 16,
2014 (updated Oct. 17, 2014), http://azc.cc/1waaUm9.
                               6
assuring the City that it was “an important player in this
process.” J.A. 750-51. But the agency also said it could not
reinstate the routes in place before September 18, 2014,
because that would require a time-consuming series of related
changes to air-traffic control and aircraft automation systems,
as well as additional safety and environmental reviews. The
FAA also declined the Preservation Officer’s request to re-
open environmental review of the new routes.

     In mid-February and again in early April the following
year, the City submitted data to the FAA purporting to show
that the agency’s assertions to the Preservation Officer
regarding the noise impact of the new routes were “massive[ly]
and material[ly]” incorrect. J.A. 814. The City also alleged that
computer modeling the FAA was required to use under its own
regulations showed that 40,000 additional residents would be
exposed to noise loud enough to disrupt speech compared to
before the new routes were implemented. And the City
renewed its request that the FAA reopen a statutorily mandated
consultation process with the State Preservation Office, in
order to provide the City with data from the FAA’s modeling,
conduct an environmental review of the route changes, and find
ways to either minimize the noise impact of those changes or
restore the old routes.

     In mid-April the FAA responded with a letter to the City
that included the Working Group’s final report. The report
evaluated alternative routes and amended some existing routes
but reaffirmed the agency’s decision not to conduct further
review of the new flight paths’ environmental impact. And
though the accompanying letter expressed the FAA’s
frustration that the City had offered no alternative route
proposals, the letter also conveyed the agency’s promise to
consider further modifications as it “continue[d] to support a
collaborative approach towards addressing the community’s
                                7
concerns.” J.A. 1036. The letter did not address the City’s data,
modeling, or requests. In fact, the accompanying documents
disclosed that noise level reduction was not among the
Working Group’s stated objectives.

     The City’s response expressed frustration that despite
initial promises, the FAA had organized the Working Group so
that it would not address the noise issue, and had even excluded
the City from meetings for fear of confrontation between the
City and the airlines. Indeed, the City was not listed as a
Working Group member. The City also protested that it had
provided an alternative plan to the FAA—namely, reinstating
the original routes but continuing to use satellite technology—
which the City claimed would eliminate the 69% increase in
residents exposed to higher noise levels and cost airlines only
$700,000 more per year in fuel compared to the new routes.

      In late May, the City met with the FAA and the airlines to
again discuss ways to fix the noise issues. The FAA
characterized these discussions as “productive” in a follow-up
letter sent on June 1. J.A. 1109. The letter also listed short-term
adjustments the agency could make within six months, as well
as some “longer term” possibilities, which the agency could
implement within a year following additional environmental
review. Id. The letter said nothing about the City’s data
submissions, previous requests to reopen consultation and
environmental review, proposal to return to the old routes while
still using satellite technology, or exclusion from the Working
Group.

     Also on June 1, the City sought review in our court,
characterizing the FAA’s last letter as a final order. The
Historic Neighborhoods filed their own petition for review in
late July. The FAA moved to dismiss these petitions as
untimely.
                               8
                               II

     We must first determine whether these petitions are
untimely. A petition for review of an FAA order must be filed
in the Court of Appeals “not later than 60 days after the order
is issued.” 49 U.S.C. § 46110(a). The parties disagree over
when this sixty-day clock began to run—i.e., when the FAA’s
decision regarding the new flight routes crystallized into final
agency action. The answer is relevant because only a final
action can be a reviewable “order” within the meaning of
section 46110’s sixty-day deadline. See Flytenow, Inc. v. FAA,
808 F.3d 882, 888-89 (D.C. Cir. 2015). A final order is one that
“mark[s] the consummation of the agency’s decisionmaking
process” and that either determines “rights or obligations” or is
a source of “legal consequences.” Friedman v. FAA, 841 F.3d
537, 541 (D.C. Cir. 2016) (quoting Bennett v. Spear, 520 U.S.
154, 177-78 (1997)).

     The FAA contends that its final “order” regarding the new
routes issued on September 18, 2014, when the routes were
formally published and put into effect. We agree. The
September 2014 publication was a final order because it
satisfies both prongs of the finality test.

     First, the September publication marked “the
consummation of the agency’s decisionmaking process,” id.,
because it put the new routes into effect following extensive
testing and evaluation intended to ensure that those routes
would be safe and consistent with air traffic requirements, see
Fed. Aviation Admin., Order No. 7100.41, Performance Based
Navigation Implementation Process §§ 2-3 to 2-6 (2014).

     Petitioners respond that although the new routes went into
effect in September, the agency’s decisionmaking process
regarding those routes had not yet concluded. See Friedman,
                               9
841 F.3d at 541. Petitioners note that the FAA’s process for
developing new routes actually has five steps, of which
publication of the new routes was only the fourth. The fifth step
provides for post-implementation monitoring and review,
which, petitioners contend, could have led to further route
changes.

     But this final step is not part of the agency’s
“decisionmaking process.” Id. (emphasis added). Rather, it
consists of “Monitoring and Evaluation” of decisions already
“[i]mplement[ed],” see Order 7100.41, supra, § 2-7, “to
ensure” that those decisions play out “as expected,” id. To be
sure, that monitoring might lead to adjustments to the new
routes, but by then the primary development of those routes has
already happened. Cf. Friedman, 841 F.3d at 543 (explaining
that “a vague prospect of reconsideration” does not defeat a
finding of finality).

     As for the second prong of the finality test, it was the
September publication, and not the June 1 letter or any of the
agency’s other reports or communications, that determined
“rights [and] obligations” and produced “legal consequences.”
Id. at 541. And it was the September publication that led to the
effects petitioners now seek to reverse: increased noise in
certain areas of Phoenix. We also note that the relief requested
by petitioners is “vacat[ur] and remand [of the] FAA’s decision
to implement the [new flight] routes”—that is, of the
September order. Phoenix Br. 61. Thus, petitioners implicitly
recognize that the September publication, and only that
publication, determined the legal consequences they wish to
challenge. We therefore conclude that the September 18, 2014
publication of the new flight routes was the relevant final
“order.”
                                 10
     The petitions thus came more than half a year too late. The
review statute, however, provides that a court may allow a
petition to be filed after the usual deadline “if there are
reasonable grounds for not filing by the 60th day.” 49 U.S.C.
§ 46110(a). While we “rarely [find] ‘reasonable grounds’
under section 46110(a),” Elec. Privacy Info. Ctr. v. FAA, 821
F.3d 39, 43 (D.C. Cir. 2016), we have done so in cases quite
similar to this one.

     For instance, in Paralyzed Veterans of America v. Civil
Aeronautics Board, the Board promulgated a final rule but
“explicitly left its rulemaking docket open in order to receive
additional comments from the public.” 752 F.2d 694, 705 n.82
(D.C. Cir. 1985), rev’d on other grounds sub nom. U.S. Dep’t
of Transp. v. Paralyzed Veterans of Am., 477 U.S. 597 (1986).
“Aware that the rule might be undergoing modification, and
unable to predict how extensive any modifications would be,
petitioners elected to wait until the regulation was in final form
before seeking review,” six months after the final rule had been
published. Id. We found that petitioners had shown “reasonable
grounds” for late filing under a review statute materially the
same as the one at issue here. 4 See id. (citing 49 U.S.C.
§ 1486(a) (1976)). In doing so, we observed that “[a]ny delay
simply served properly to exhaust petitioners’ administrative
remedies, and to conserve the resources of both the litigants
and this court.” Id.

    Similarly, in Safe Extensions, Inc. v. FAA, after the FAA’s
publication of an advisory circular establishing certain

     4
       In Paralyzed Veterans, the petitioners had filed a petition for
review within sixty days of an amended final order. But the
Paralyzed Veterans court treated that fact as a distinct reason to
review the petition, considering “[m]ore important[]” the fact that
petitioners had shown reasonable grounds for delaying their petition
for review of the original order. See 752 F.2d at 705 n.82.
                                11
requirements for manufacturing products provoked a
“significant uproar in the industry,” the FAA told the industry
to ignore the existing order pending a revision. 509 F.3d 593,
603 (D.C. Cir. 2007). The petitioner, “[b]ased on these
representations, and hoping to avoid litigation,” decided to wait
and see if the agency would address the petitioner’s concerns
voluntarily. Id. As a result, we found reasonable grounds for
the petitioner’s late filing. Id. at 604.

     To be sure, in Safe Extensions the FAA had expressly
directed the petitioner to ignore the final order, whereas here
the FAA merely promised to look into possible modifications.
But the key in Safe Extensions was that the agency left parties
“with the impression that [it] would address their concerns” by
replacing its original order with a revised one. Id. at 596. There
we were concerned that the agency’s comments “could have
confused the petitioner and others.” Id. at 603.

     Those same concerns are present here. The FAA
repeatedly communicated—in an October public meeting, in a
November letter, in a December public meeting, in a January
letter, in a February decision to reconvene the Working Group,
in an April letter, and in a May meeting with city officials—
that the agency was looking into the noise problem, was open
to fixing the issue, and wanted to work with the City and others
to find a solution. This pattern would certainly have led
reasonable observers to think the FAA might fix the noise
problem without being forced to do so by a court. And given
the FAA’s serial promises, petitioning for review soon after the
September order might have shut down dialogue between the
petitioners and the agency. See Oral Arg. Tr. 58:8-13. We do
not punish the petitioners for treating litigation as a last rather
than a first resort when an agency behaves as the FAA did here.
See Paralyzed Veterans, 752 F.2d at 705 n.82.
                                12
     While we rarely find a reasonable-grounds exception, this
is such a rare case. We hold that petitioners had reasonable
grounds for their delay in filing. To conclude otherwise would
encourage the FAA to promise to fix a problem just long
enough for sixty days to lapse and then to argue that the
resulting petitions were untimely. We therefore reach the
merits of the petitions.

                                III

     The petitioners argue that the FAA’s approval of the new
flight routes was arbitrary and capricious and violated the
National Historic Preservation Act, the National
Environmental Policy Act, the Department of Transportation
Act, and the FAA’s Order 1050.1E. We agree.5

                                 A

     Under the National Historic Preservation Act, federal
agencies must “account [for] the effect of their actions on
structures eligible for inclusion in the National Register of
Historic Places.” Ill. Commerce Comm’n v. ICC, 848 F.2d
1246, 1261 (D.C. Cir. 1988). In fulfilling this obligation,
agencies must consult with certain stakeholders in the
potentially affected areas, including representatives of local
governments. See 36 C.F.R. § 800.2(a)(4), (c)(3). If an agency
determines that no historic structures will be adversely
affected, it still has to “notify all consulting parties”—
including a representative of the local government—and give
them any relevant documentation. Id. § 800.5(c).
    5
       Petitioners also claim that the FAA violated the agency’s own
Order 7100.41 by excluding the City from the Working Group re-
convened in the wake of the controversy over the new routes. We do
not reach that argument, however, because our review is limited to
the agency’s September order.
                               13

     Here the FAA failed to fulfill these obligations because it
consulted only low-level employees in the City’s Aviation
Department, whom the City had never designated as its
representatives. True, the City never informed the FAA that
low-level Aviation Department employees were inadequate
points of contact, but that is irrelevant. Neither statute nor
regulation imposes a duty on local governments to
affirmatively inform the agency of their chosen representatives.
Just the opposite: the agency must ask local governments who
their authorized representatives are. See id. § 800.3(f), (f)(1).
The FAA never took that step here. And the FAA’s failure to
notify and provide documentation to the City of the agency’s
finding of no adverse impact violated regulations under the
Preservation Act, and denied the City its right to participate in
the process and object to the FAA’s findings. See id.
§§ 800.2(c)(3), 800.5(c)(2).

     Additionally, unless confidential information is involved,
agencies must “provide the public with information about an
undertaking and its effects on historic properties and seek
public comment and input.” Id. § 800.2(d)(2) (emphasis
added). The FAA admits, however, that it did not make “local
citizens and community leaders” aware of the proposed new
routes and procedures, J.A. 364, and it does not claim that any
confidentiality concerns applied.

     Further, by keeping the public in the dark, the agency
made it impossible for the public to submit views on the
project’s potential effects—views that the FAA is required to
consider. See 36 C.F.R. § 800.5(a); see also Am. Bird
Conservancy v. FCC, 516 F.3d 1027, 1035 (D.C. Cir. 2008)
(“Interested persons cannot request an [environmental
assessment] for actions they do not know about, much less for
actions already completed.”).
                               14

                                B

     Under the National Environmental Policy Act (NEPA),
federal agencies must assess and disclose the environmental
impacts of “major” actions prior to taking those actions. 42
U.S.C. § 4332(2)(C); 40 C.F.R. § 1502.1. This process
“ensures” that before an agency acts, it will “have available”
and “carefully consider[] detailed information concerning
significant environmental impacts.” Robertson v. Methow
Valley Citizens Council, 490 U.S. 332, 349 (1989). The process
also “guarantees that the relevant information will be made
available to the larger audience that may also play a role in both
the decision-making process and the implementation of [the]
decision.” Id.

     NEPA’s requirements vary based on the type of agency
action in question. Actions with significant environmental
effects require a full environmental-impact statement. Actions
with impacts that are not significant or are unknown require a
briefer environmental assessment. And actions “which do not
individually or cumulatively have a significant effect on the
human environment” can be categorically excluded from any
environmental review. 40 C.F.R. § 1508.4.

     However, the FAA may not categorically exclude an
action from environmental review if “the Administrator
determines that extraordinary circumstances” would counsel
otherwise. FAA Modernization and Reform Act of 2012, Pub.
L. No. 112-95, § 213(c)(1), 126 Stat. 11, 49. Under the FAA’s
own regulations, extraordinary circumstances exist when an
action’s effects “are likely to be highly controversial on
environmental grounds.” Fed. Aviation Admin., Order No.
1050.1E, Environmental Impacts: Policies and Procedures
¶ 304i (2004). Here, the FAA found that the new routes were
                              15
“not likely to be highly controversial on environmental
grounds,” and thus determined that no extraordinary
circumstances existed. That determination was arbitrary and
capricious.

     The FAA’s determination was arbitrary in light of the
agency’s admitted failure to notify “local citizens and
community leaders” of the proposed new routes before they
went into effect. J.A. 364, 367. This failure made it impossible
for the FAA to take into account “[o]pposition on
environmental grounds by a . . . State, or local government
agency or by . . . a substantial number of the persons affected
by the [FAA’s] action.” Order 1050.1E, supra, ¶ 304i; cf. Am.
Bird Conservancy, 516 F.3d at 1035 (faulting the agency for its
lack of diligence in informing and involving the public since
“[i]nterested persons cannot request an [environmental
assessment] for actions they do not know about, much less for
actions already completed”).

     The FAA argues that it was reasonable simply to assume
that its proposal would not be controversial on environmental
grounds, given that the agency had “confirmed that no
significant noise impacts were anticipated at all, received the
concurrence of the State Historic Preservation Officer[,] who
expressed no concerns, and then further discussed the finding
with the Airport Authority[,] [which] also expressed no
concerns.” FAA Br. 80. Common sense reveals otherwise. As
noted, the FAA’s proposal would increase by 300% the number
of aircraft flying over twenty-five historic neighborhoods and
buildings and nineteen public parks, with 85% of the new flight
traffic coming from jets. The idea that a change with these
effects would not be highly controversial is “so implausible”
that it could not reflect reasoned decisionmaking. See Motor
Vehicle Mfrs. Ass’n of U.S. v. State Farm Mut. Auto. Ins. Co.,
463 U.S. 29, 43 (1983).
                                16

      The FAA also erred by deviating from its usual practice in
assessing when new flight routes are likely to be highly
controversial, without giving a “reasoned explanation for . . .
treating similar situations differently.” W. Deptford Energy,
LLC v. FERC, 766 F.3d 10, 20 (D.C. Cir. 2014). In assessing
proposed route changes at airports in Boston, Northern
California, Charlotte, and Atlanta, the FAA has relied on its
general observation that a proposal is likely to be highly
controversial if it would increase sound levels by five or more
decibels in an area already experiencing average levels of 45-
60 decibels. But here the agency said exactly the opposite and
never explained its about-face. The FAA replies that “[e]ach
airport is different and the potential effects of any changes at
those airports will differ as well.” FAA Br. 81. But that does
not explain how the Phoenix plan could be less likely to stir
controversy than other plans that had the same projected
impact. Thus, the agency acted arbitrarily in departing from its
usual determinations regarding when a projected noise increase
is likely to be highly controversial.

     In short, the FAA had several reasons to anticipate that the
new flight routes would be highly controversial: The agency
was changing routes that had been in place for a long time, on
which the City had relied in setting its zoning policy and
buying affected homes. The air traffic over some areas would
increase by 300%—with 85% of that increase attributed to
jets—when before only prop aircraft flew overhead. The FAA
found a “potential [for] controversy” but did not notify local
citizens and community leaders of the proposed changes as the
agency was obligated to, much less allow citizens and leaders
to weigh in.6 And the agency departed from its determinations

    6
     Although at times it may be difficult to identify precisely who
must be notified, the FAA’s regulatory acknowledgment of its
                                 17
in materially identical cases. Thus, the FAA acted arbitrarily in
finding under Order 1050.1E that the new routes were unlikely
to be highly controversial and could thus be categorically
excluded from further environmental review.

                                 C

    Petitioners also raise two claims related to the
Transportation Act’s section 4(f). First, they argue that the
FAA violated its duty to consult with the City in assessing
whether the new routes would substantially impair the City’s
parks and historic sites. Second, petitioners claim that the FAA
was wrong to find that the routes would not substantially impair
these protected areas. We agree on both points.

                                  i

     Section 4(f) of the Transportation Act calls for “special
effort[s] to preserve the natural beauty of . . . public park and
recreation lands . . . and historic sites.” 49 U.S.C. § 303(a). To
that end, the FAA’s regulations require it to consult “all
appropriate . . . State[] and local officials having jurisdiction
over the affected section 4(f)” areas when assessing whether a
noise increase might substantially impair these areas. Order
1050.1E, supra, ¶ 6.2e (emphases added). According to the
City, the agency violated this requirement by not consulting the
proper city officials about the proposed flight routes in
Phoenix. Cf. Nat’l Conservative Political Action Comm. v.
FEC, 626 F.2d 953, 959 (D.C. Cir. 1980) (“Agencies are under

obligation has narrowed the field. Here, given the changes about to
occur, it was unreasonable to ignore elected local officials once the
FAA was on notice that the Aviation Department employee lacked
authorization to speak for the City of Phoenix. See infra Part III.C
(discussing FAA regulations under section 4(f) of the Transportation
Act).
                                18
an obligation to follow their own regulations, procedures, and
precedents, or provide a rational explanation for their
departures.”).

      The FAA responds that it did consult employees in the
City’s Aviation Department, and that at the time the City didn’t
tell the agency what the City now asserts: that those employees
lacked authority to speak for the City regarding the new flight
routes. Thus, the FAA contends, its failure to consult other
local officials was not arbitrary.

     We are not persuaded. As noted, the FAA spoke mainly
with one low-level employee in the City’s Aviation
Department and occasionally with other low-ranking members
of the department. But it was unreasonable for the agency
simply to assume that low-level Aviation Department
employees had jurisdiction over the historic sites and public
parks protected by section 4(f), much less that these employees
(along with the State Historic Preservation Officer) represented
all the local officials with such jurisdiction, as the agency’s
consultation duties required. Besides, the FAA cites no
evidence that it consulted with these City officials on historic
sites and public parks in particular. Thus, the FAA’s
consultation process was arbitrarily confined.

                                 ii

     Section 4(f) also provides that a federal transportation
project may “use” a public park or historic site only if “there is
no prudent and feasible alternative to using that land.” 49
U.S.C. § 303(c)(1). A project makes “constructive use” of a
protected area if the project would “substantially impair” that
area. Order 1050.1E, supra, ¶ 6.2e. And a project substantially
impairs an area if it “substantially diminish[es]” the “activities,
features, or attributes . . . that contribute to its enjoyment.” Id.
                                19
¶ 6.2f. For instance, a project would make constructive use of
a park if it subjected the park to aircraft noise “at levels high
enough to have negative consequences of a substantial nature
that amount to a taking.” Id. In that case, the project could
lawfully proceed only if there was no prudent and feasible
alternative to using the park.

     In determining whether a transportation project would
substantially impair an area protected under section 4(f), the
FAA may rely on guidelines set forth in 14 C.F.R. pt. 150 (the
Part 150 guidelines), including the directive “to evaluate
impacts on historic properties that are in use as residences.”
Order 1050.1E, supra, ¶ 6.2h. But the Part 150 guidelines “may
not be sufficient to determine the noise impact” on historic
residences if “a quiet setting is a generally recognized purpose
and attribute” of those residences. Id. (emphasis added). Here
the FAA found that a quiet setting was not a recognized
purpose of the affected historic homes, neighborhoods, and
sites, so the agency relied only on the Part 150 guidelines in
assessing the noise impact on those sites. And on that basis, it
concluded that the increased noise would not substantially
impair the historic buildings and areas in question.

     The City contends that it was unreasonable for the FAA to
rely only on the Part 150 guidelines, because the agency didn’t
have enough information to tell if the areas affected here were
generally recognized as quiet settings. We agree.

     As evidence that these sites were not “generally
recognized” as quiet settings, the FAA pointed to the sites’
urban location. Id. But that isn’t enough: even in the heart of a
city, some neighborhoods might be recognized as quiet oases.
The agency also observed that planes were flying over the
affected historic sites even before the new routes took effect.
But those earlier flights involved propeller aircraft that flew far
                               20
less often, so the homes beneath them might still have been
generally recognized as “quiet setting[s].” Id.

     Thus, it was unreasonable for the agency to rely only on
the Part 150 guidelines in concluding that noise from the new
flight routes would not substantially impair the affected historic
sites. As a result, that conclusion lacks substantial supporting
evidence. For both these reasons, we find that the agency’s
substantial-impairment analysis was arbitrary and capricious.
See BFI Waste Sys. of N. Am. v. FAA, 293 F.3d 527, 532 (D.C.
Cir. 2002) (observing that an agency’s action is arbitrary and
capricious if it is “‘not supported by substantial evidence’ in
the record as a whole” (quoting Motor Vehicle Mfrs. Ass’n of
U.S. v. Ruckelshaus, 719 F.2d 1159, 1164 (D.C. Cir. 1989)));
see also State Farm, 463 U.S. at 43 (“We may not supply a
reasoned basis for the agency’s action that the agency itself has
not given.” (quoting SEC v. Chenery Corp., 332 U.S. 194, 196
(1947))).

                               IV

    For the foregoing reasons, we grant the petitions, vacate
the September 18, 2014 order implementing the new flight
routes and procedures at Sky Harbor International Airport, and
remand the matter to the FAA for further proceedings
consistent with this opinion.

                                                     So ordered.
    SENTELLE, Senior Circuit Judge, dissenting:

     I respectfully dissent from the majority’s opinion in this
case, not because I disagree with the merits but because I
believe the court should not reach them. I therefore express no
opinion on the merits and instead disembark at the question of
timeliness.

     As the majority acknowledges, petitions for review of an
FAA order must be filed “not later than 60 days after the order
is issued.” 49 U.S.C. § 46110(a); see Maj. Op. at 8.
Nevertheless, as my colleagues note, the petitions in this case
were filed “more than half a year too late.” Maj. Op. at 10.
Such late filing is excused “only if there are reasonable grounds
for not filing” within the 60-day period. § 46110(a); see Maj.
Op. at 10. The majority relies on two cases, Paralyzed
Veterans of America v. Civil Aeronautics Board, 752 F.2d 694
(D.C. Cir. 1985), rev’d on other grounds sub nom. U.S. Dep’t
of Transp. v. Paralyzed Veterans of Am., 477 U.S. 597 (1986),
and Safe Extensions, Inc. v. FAA, 509 F.3d 593 (D.C. Cir.
2007), for its conclusion that reasonable grounds exist in the
present case. See Maj. Op. at 10-12. Both cases, however, are
distinguishable.

     As my colleagues in the majority acknowledge, in
Paralyzed Veterans, “the Board promulgated a final rule but
‘explicitly left its rulemaking docket open in order to receive
additional comments from the public.’” Maj. Op. at 10 (citing
Paralyzed Veterans, 752 F.2d at 705 n.82). This unusual
circumstance, prompting the petitioners to wait for further
changes to the rule before filing for review, constituted
reasonable grounds within the meaning of § 46110(a). And,
as the majority acknowledges in discussing Safe Extensions,
that case involved the FAA instructing parties to ignore an
order as it would be modified and revised. Safe Extensions,
509 F.3d at 603; Maj. Op. at 10-11. The petitioner accordingly
waited to file and, given that unique context, we concluded
                               2
reasonable grounds existed for delayed filing. Safe Extensions,
509 F.3d at 604. These factual contexts are distinguishable
from the present case, in which the FAA never promised to
suspend the existing order and explicitly had the new flight
paths continue while it considered the possibility of future
changes. Mere agency acknowledgment of the possibility of
future modification is not a rare circumstance; Paralyzed
Veterans and Safe Extensions are instead the truly rare
circumstances of an agency explicitly inducing warranted
delay by a putative petitioner. Agencies are often welcome to
re-initiate the decision-making process at some future point and
to follow the necessary procedures to change their minds —
this mere possibility, or even the mention of it, cannot be
enough to excuse a petitioner’s failure to file within the
statutorily mandated 60-day period. Otherwise, the statutory
limit would cease to have meaning.

     Instead, as we observed in Electronic Privacy Information
Center v. FAA, 821 F.3d 39, 43 (D.C. Cir. 2016), “[w]e have
rarely found ‘reasonable grounds’ under section 46110(a).”
Safe Extensions (and, by comparison, Paralyzed Veterans) is
the “rare instance[]” of such reasonable grounds, not the rule.
Nat’l Fed’n of the Blind v. U.S. Dep’t of Transp., 827 F.3d 51,
57 (D.C. Cir. 2016). Because reasonable grounds are so
infrequent, the onus is almost always on the petitioners to
protect themselves and file within the 60-day timeframe. The
FAA’s failure to act with perfect clarity is not sufficient to
remove petitioners’ duty to protect themselves. See, e.g., Nat’l
Fed’n of the Blind, 827 F.3d at 57-58; Elec. Privacy Info. Ctr.,
821 F.3d at 42-43; Avia Dynamics, Inc. v. FAA, 641 F.3d 515,
521 (D.C. Cir. 2011). Mere confusion over where or when to
file, lack of clarity by the FAA in its communications,
ignorance, and lack of notice do not suffice, at least
independently, to qualify as reasonable grounds for delay under
§ 46110(a) and our precedent. See Nat’l Fed’n of the Blind,
                               3
827 F.3d at 57-58; Elec. Privacy Info. Ctr., 821 F.3d at 42-43;
Avia Dynamics, 641 F.3d at 521. Such grounds are rare and
found in unique circumstances, such as Safe Extensions and
agency procurements of delay by promising a new order and
instructing parties to ignore the prior one, or Paralyzed
Veterans and an agency leaving its rulemaking docket open
during the modification process, where delay “simply served
properly to exhaust petitioners’ administrative remedies,” 752
F.2d at 705 n.82. No such unusual facts are in the present case.
I would determine that petitioners lacked reasonable grounds
for untimely filing.

     I note in passing the majority’s references to petitioners’
notice and knowledge of the FAA’s proceedings having come
through “low-level” employees. See Maj. Op. at 3-4, 13. I do
not see that this can help establish reasonable grounds for any
delay, let alone one stretching six months beyond the 60-day
statutory provision. There was ample time for the higher-ups
to gain and act on adequate knowledge.

     In concluding that petitioners did not have reasonable
grounds for waiting six months to file for review, I do not
contend that the FAA acted with perfect clarity at all times.
However, the record does not suggest to me that petitioners had
a clear reason, akin to those rare instances present in Paralyzed
Veterans and Safe Extensions, to forego at the very least a
protective filing. For this reason, I would decide this case on
the question of timeliness, deny the petitions for review, and
decline to reach the merits of their arguments.
