                  FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

ASSOCIATION OF FLIGHT                   
ATTENDANTS, CWA, AFL-CIO,
                                              No. 07-17232
                  Plaintiff-Appellee,
                                                D.C. No.
                 v.
                                           CV-07-00921-PHX-
MESA AIR GROUP, INC.; MESA                        ROS
AIRLINES, INC.; FREEDOM AIRLINES
                                                OPINION
INC.; GO AIRLINES, INC.,
            Defendants-Appellants.
                                        
        Appeal from the United States District Court
                 for the District of Arizona
         Roslyn O. Silver, District Judge, Presiding

                  Argued and Submitted
          February 11, 2009—Stanford, California

                      Filed June 1, 2009

    Before: Dorothy W. Nelson, William A. Fletcher and
            Richard C. Tallman, Circuit Judges.

           Opinion by Judge William A. Fletcher




                             6511
                AFA v. MESA AIR GROUP            6513




                     COUNSEL

Edward Gilmartin, Deirdre E. Hamilton, ASSOCIATION OF
FLIGHT ATTENDANTS-CWA, AFL-CIO, Washington,
6514               AFA v. MESA AIR GROUP
D.C., Michael J. Keenan, WARD, KEENAN & BARRETT,
Phoenix, Arizona, for the plaintiff-appellee.

Joseph L. Manson, III, Marc A. Antonetti, BAKER &
HOSTETLER, LLP, Washington, D.C., Stephanie J. Quincy,
Bennett Evan Cooper STEPTOE & JOHNSON, LLP, Phoe-
nix, Arizona, for the defendants-appellants.


                          OPINION

W. FLETCHER, Circuit Judge:

   Defendant Mesa Airlines (“Mesa”) appeals the grant of a
preliminary injunction in favor of Plaintiff Association of
Flight Attendants (“AFA”). AFA and Mesa are parties to col-
lective bargaining agreements (“CBAs”) that have expired.
They are now in the process of bargaining for new agree-
ments. AFA brought this suit after Mesa changed the applica-
ble Federal Aviation Administration (“FAA”) regulations
(“FARs”) for its scheduling of flight attendants. Previously,
Mesa had used those designed for flight crews; after the
change, it used those designed for flight attendants.

   AFA contends that the Railway Labor Act (“RLA”), 45
U.S.C. § 151 et seq., prevents Mesa’s unilateral change to the
union’s status quo working conditions. It contends that its dis-
agreement with Mesa over the change is a “major dispute”
within the meaning of the RLA, and that it may therefore seek
an injunction in federal district court against the change. Mesa
contends that the terms of the parties’ CBAs permit it to make
the change, and that its disagreement with AFA is a “minor
dispute” within the meaning of the RLA for which the exclu-
sive remedy is binding arbitration.

  The district court held that the disagreement is a major dis-
pute and granted a preliminary injunction against Mesa. Mesa
                   AFA v. MESA AIR GROUP                   6515
has brought an interlocutory appeal over which we have
appellate jurisdiction under 28 U.S.C. § 1292(a)(1). We hold
that the dispute is a minor dispute within the meaning of the
RLA. We therefore vacate the preliminary injunction and
remand to the district court with directions to dismiss for lack
of subject matter jurisdiction.

                       I.   Background

   AFA and Mesa are parties to two CBAs that ran through
June 13, 2006. The CBAs set forth the parties’ rights and obli-
gations with respect to the employment of AFA members by
Mesa. Under an RLA-mandated process, the parties have been
in negotiations and mediation to replace these CBAs. Until
new CBAs can be agreed upon, the old CBAs have continued
in effect, as mandated by Section 6 of the RLA. 45 U.S.C.
§ 156.

   This case arises out of a dispute over the application of
FAA regulations to the scheduling of flight attendants. The
FAA has promulgated regulations limiting the allowable work
schedules for various airline employees, titled “Flight Time
Limitations and Rest Requirements,” or FARs. The regula-
tions include FARs for flight crewmembers, 14 C.F.R.
§ 121.471 (“Pilot FARs”), and flight attendants, id. § 121.467
(“Flight Attendant FARs”). The Flight Attendant FARs per-
mit an airline to schedule its flight attendants according to
either the guidelines established in the Flight Attendant FARs
or those in the Pilot FARs. Id. § 121.467(c).

   During the duration of the CBAs, from 1995 through 2006,
Mesa scheduled its flight attendants in accordance with the
Pilot FARs. On September 19, 2006, AFA presented a pro-
posal to Mesa seeking to amend the CBAs by incorporating
specific duty time and rest provisions in the contracts. Mesa
rejected this proposal. In 2007, Mesa unilaterally adjusted
scheduling for flight attendants to accord with the Flight
Attendant FARs rather than the Pilot FARs.
6516               AFA v. MESA AIR GROUP
   AFA filed suit under the RLA to enjoin Mesa from imple-
menting this change until bargaining had been exhausted.
Mesa filed a motion to dismiss for lack of subject matter juris-
diction, which the district court denied on October 1, 2007.
Mesa filed a motion to reconsider on October 16, 2007, pre-
senting new evidence on the question of subject matter juris-
diction. The district court granted AFA’s motion for a
preliminary injunction on October 17, 2007, and denied
AFA’s motion for reconsideration on December 13, 2007.
The district court held that the CBAs contain an implied term
that applies the Pilot FARs to flight attendants, and that Mesa
cannot now unilaterally alter this term.

  Mesa filed this interlocutory appeal.

                  II.    Standard of Review

   We review de novo, as a question of law and of subject
matter jurisdiction, whether a dispute is major or minor under
the Railway Labor Act. Polich v. Burlington N., Inc., 942
F.2d 1467, 1469 (9th Cir. 1991); Air Line Pilots Ass’n, Int’l
v. Alaska Airlines, Inc. (“Alaska Airlines”), 898 F.2d 1393,
1395 (9th Cir. 1990). We also review de novo the construc-
tion of a CBA. Carpenters Health & Welfare Trust Fund for
Cal. v. Bla-Delco Constr., Inc., 8 F.3d 1365, 1367 (9th Cir.
1993).

                        III.   Discussion

   [1] Labor relations between Mesa and AFA are governed
by the RLA. The RLA mandates a long process of negotiation
and mediation before unions and common carriers are permit-
ted to use their various economic weapons to pressure the
other side to reach an agreement. 45 U.S.C. § 151 et seq. As
relevant to this case, the RLA provides two separate dispute
resolution procedures that the parties to a labor negotiation
can invoke during the negotiation process. Consol. Rail Corp.
v. Ry. Labor Executives’ Ass’n (“Conrail”), 491 U.S. 299,
                   AFA v. MESA AIR GROUP                       6517
302-04 (1989). One set of procedures applies to what are
labeled “major disputes” between the parties. The other set
applies to what are labeled “minor disputes.” Id.

   [2] Major disputes generally result from attempts by labor
or management to impose new obligations or create new
rights. Id. at 302. Major disputes must be settled through an
extended bargaining process. Id. at 302-03. Federal district
courts may issue injunctions to freeze the status quo during
the bargaining process over such disputes. Id. at 303; Alaska
Airlines, 898 F.2d at 1396. Minor disputes, on the other hand,
generally result from attempts to enforce existing contractual
obligations and rights. Conrail, 491 U.S. at 302; Alaska Air-
lines, 898 F.2d at 1396. Such disputes are subject to exclusive
binding arbitration before the National Railroad Adjustment
Board. Conrail, 491 U.S. at 303-04; Alaska Airlines, 898 F.2d
at 1396.

   When a dispute is minor, the parties have no duty to main-
tain the status quo. Bhd. of Locomotive Eng’rs v. Burlington
N. R.R., 838 F.2d 1102, 1111 (9th Cir. 1988) (Pregerson, J.,
concurring). Minor disputes are not necessarily unimportant
or insignificant. Indeed, minor disputes can involve disagree-
ments of great practical or economic significance. Int’l Bhd.
of Teamsters v. Sw. Airlines Co., 875 F.2d 1129, 1133 (5th
Cir. 1989) (en banc).

  The Supreme Court has elaborated on the distinction
between major and minor disputes. Minor disputes

    contemplate[ ] the existence of a collective agree-
    ment already concluded or, at any rate, a situation in
    which no effort is made to bring about a formal
    change in terms or to create a new one. The dispute
    relates either to the meaning or proper application of
    a particular provision with reference to a specific sit-
    uation or to an omitted case. In the latter event the
    claim is founded upon some incident of the employ-
6518               AFA v. MESA AIR GROUP
    ment relation, or asserted one, independent of those
    covered by the collective agreement, e.g., claims on
    account of personal injuries. In either case the claim
    is to rights accrued, not merely to have new ones
    created for the future.

Conrail, 491 U.S. at 303 (quoting Elgin, Joliet & E. Ry. Co.
v. Burley, 325 U.S. 711, 723 (1945)).

   [3] The distinction between major and minor disputes
“looks to whether a claim has been made that the terms of an
existing agreement either establish or refute the presence of a
right to take the disputed action. The distinguishing feature of
such a case is that the dispute may be conclusively resolved
by interpreting the existing agreement.” Id. at 305. When “an
employer asserts a contractual right to take the contested
action, the ensuing dispute is minor if the action is arguably
justified by the terms of the parties’ collective-bargaining
agreement. Where, in contrast, the employer’s claims are friv-
olous or obviously insubstantial, the dispute is major.” Id. at
307. The burden to establish that an action is “arguably justi-
fied” by the terms of the CBA is “relatively light.” Id. When
in doubt, courts construe disputes as minor. Bhd. of Locomo-
tive Eng’rs, 838 F.2d at 1111.

   We hold that Mesa has carried its burden to show that its
action is “arguably justified” by the terms of the existing
CBAs. We therefore hold that the dispute is minor and subject
to the exclusive arbitral remedy of the RLA.

   [4] The CBAs at issue refer only to “the F.A.R.s” or “the
applicable FAR maximum.” The provisions within the CBAs
do not explicitly establish which of the two FARs is to be
applied to flight attendant schedules. Residual authority
clauses in the CBAs provide that “the Company retains all
authority and rights to manage its operations and direct its
Flight Attendants work force” to the extent not “expressly
restricted by the CBA.” “Management rights” clauses in the
                   AFA v. MESA AIR GROUP                  6519
CBAs reserve to Mesa “without limitation” the right to “es-
tablish and, from time to time, amend, suspend or revoke
rules, regulations and procedures . . . [and] to establish new
routes, services, schedules and areas of service.”

   Mesa argues that the ambiguity in the CBAs over which
FARs apply to flight attendant schedules, combined with the
explicit delegation of residual and management powers to the
employer, gives Mesa the authority to change the applicable
FARs unilaterally. Mesa supports this argument with testi-
mony of Patricia Dravis, who negotiated one of the CBAs on
behalf of AFA. Dravis testified that she believed the CBA
gave Mesa the authority to switch from the Pilot FARs to the
Flight Attendant FARs without consent of the AFA.

   [5] Two other circuits have held in similar circumstances
that the existence of a broad management rights clause is
enough to create an “arguable” question of contract interpreta-
tion when a CBA does not explicitly establish rules or policies
governing working conditions. In Airline Professionals Ass’ns
of the International Brotherhood of Teamsters, Local Union
No. 1224, AFL-CIO v. ABX Air, Inc., 274 F.3d 1023 (6th Cir.
2001), management unilaterally imposed a policy of random
searches of employees in order to prevent theft. The union
objected to these searches, eventually filing suit in federal
court seeking an injunction against implementation of this
policy. The Sixth Circuit held that, although “random
searches are not specifically addressed by the collective bar-
gaining agreement,” the CBA gave management “discretion
with respect to the hiring, firing, promoting, supervising,
planning, and other management functions, except as limited
by the collective bargaining agreement and public law.” Id. at
1029. Thus, it was “at least arguable that the implied terms of
the agreement permit [management] to unilaterally implement
random searches.” Id.

  [6] In International Brotherhood of Teamsters v. Southwest
Airlines Co., 875 F.2d 1129 (5th Cir. 1989) (en banc), man-
6520               AFA v. MESA AIR GROUP
agement unilaterally implemented a detailed drug and alcohol
testing policy. The Fifth Circuit held that “[o]n its face” a
clause providing that employees “shall be governed by all
Company rules, regulations and orders” not in conflict with
the terms of the agreement “at least arguably grants manage-
ment the right to enforce its policy by unilaterally promulgat-
ing rules, regulations, and orders” to govern employees. Id. at
1135. Both of these decisions reinforce our view that the man-
agement rights clauses in the CBAs here arguably provide
justification for Mesa to unilaterally interpret and apply the
ambiguous contractual language concerning the FARs.

   AFA makes two arguments. First, it argues that, because
the Pilot FARs are the status quo working conditions under
which Mesa’s flight attendants operated, they cannot be
changed unilaterally by management. AFA relies on Detroit
& Toledo Shore Line Railroad v. United Transportation
Union (“Shore Line”), 396 U.S. 142 (1969). In Shore Line,
however, neither party made an argument based on the terms
of a CBA. Id. at 147-48. Instead, management had changed
longstanding working conditions, and the union contended
that this arguably changed the status quo. Id. Management
responded by contending that the status quo was not incorpo-
rated in any CBA, and that the union was therefore not enti-
tled to an injunction to prevent management from making the
change. Id. The Court held that, in the absence of any conten-
tion based on the CBA from either side, the union could seek
an injunction preventing management from changing the prior
practice. Id.

  AFA relies upon Shore Line to argue that any status quo
working condition — whether covered by a CBA or not — is
protected by the RLA from unilateral change by management,
and that federal courts can enjoin management from making
such a unilateral change. We do not read Shore Line so
broadly. AFA’s interpretation of Shore Line would eliminate
any distinction between major and minor disputes in cases
where the union contends that management’s action violates
                    AFA v. MESA AIR GROUP                    6521
established practice, including cases where the CBA arguably
(or even clearly) allows management to change the status quo.

   AFA’s argument also ignores the Supreme Court’s decision
in Conrail. In that case, the union relied on Shore Line to
make an argument similar to AFA’s argument in this case.
The union argued that the RLA “provides a status quo obliga-
tion applicable to all minor disputes.” Conrail, 491 U.S. at
304 n.5. The Court rejected this argument, holding that in the
case of minor disputes there is no “general statutory obliga-
tion on the part of an employer to maintain the status quo
pending the Board’s decision.” Id. Before a federal court can
even reach the analysis in Shore Line — that is, before a court
can decide whether something is an established practice pro-
tected by the status quo — it must find that the disagreement
in the case is a major dispute. We do not read Conrail to over-
rule Shore Line on this point.

   Second, AFA argues (and the district court agreed) that the
application of the Pilot FARs to flight attendant schedules
constitutes an implied term of the CBAs. This argument
depends on a conclusion that the CBAs unambiguously con-
tain such an implied term. The existence of such an implied
term, if conclusively proven, would indeed prevent Mesa
from changing from the Pilot FARs to the Flight Attendant
FARs. However, the existence of such an implied term is not
clearly established in the record of this case. Therefore, the
existence of such a term is a matter of contractual interpreta-
tion that the RLA leaves exclusively to the National Railroad
Adjustment Board.

   [7] The district court found that “[a] thirteen-year history of
consistently relying on the Pilot FARs qualifies as an ‘estab-
lished and recognized custom between the parties.’ ” In so
finding, the district court relied on Brotherhood Railway Car-
men v. Missouri Pacific Railroad (“Carmen”), 944 F.2d 1422,
1429 (8th Cir. 1991). However, Carmen actually suggests the
opposite result. In Carmen, the employer argued that a dispute
6522               AFA v. MESA AIR GROUP
was “arguably justified” by the terms of a contract on the
ground that past practices could create an implied term in the
agreement. Id. at 1426. The Eighth Circuit wrote that implied
terms can arise in CBAs through past practices. Id. at 1429
(“It is well established that collective bargaining agreements
may include implied as well as express terms.”). But it held
that in the case before it, the existence of such an implied
term was debatable and should therefore be decided in arbitra-
tion. Id. (“While it is indeed arguable that practices involving
other types of rail cars at other locations may not establish
implied agreements covering the repair of freight cars at the
locations at issue, the opposite surely is also arguable.”). The
case before us appears in the same posture. Past practices
under the CBAs may or may not have created an implied
term, and there is evidence to support contentions on both
sides. The existence of an implied term is therefore arguable
and must be decided in arbitration.

                          Conclusion

   Mesa has carried its burden of showing that its change from
the Pilot FARs to the Flight Attendant FARs was arguably
justified by the CBAs. Therefore, this dispute is minor within
the meaning of the RLA, and must be decided in arbitration
before the National Railroad Adjustment Board.

  We VACATE the district court’s preliminary injunction
and REMAND to the district court with direction to DIS-
MISS for lack of subject matter jurisdiction.
