This case presents the question whether the union’s objection to the unilateral imposition of a comprehensive, mandatory drug testing program constitutes a “major” dispute under the Railway Labor Act that must be negotiated with the union before it can be implemented by Southwest Airlines, or whether the drug testing program was arguably justified by the existing collective bargaining agreement and hence was a “minor” dispute that must be arbitrated.
I
A.
Southwest Airlines Co. (“Southwest”) is a common carrier subject to the Railway Labor Act (“RLA”). The International Brotherhood of Teamsters (“the Teamsters”) represents Southwest’s mechanics and related employees. Article 2, paragraph 4 of the relevant Teamsters and Southwest collective bargaining agreement provides:
Employees covered by this Agreement shall be governed by all Company rules, regulations and orders previously or hereafter issued by proper authorities of the Company which are not in conflict with the terms and conditions of this Agreement, and which have been made available to the employee prior to becoming effective.
Before 1986, Southwest’s drug and alcohol policy consisted mainly of Rule G, a rule of many years’ standing that had been unilaterally promulgated. Its provisions defined “serious, unacceptable conduct” and included the following:
4. Reporting for or carrying on work while showing any signs of the use of intoxicants or knowingly permitting another employee to do so is strictly prohibited.
5. Possession of or drinking of any intoxicant or illegal possession or use of illegal dangerous drugs on Company premises or while in uniform and/or habitual use of intoxicants or use of illegal or dangerous drugs on or off duty will not be tolerated.
Rule G had no significant history of enforcement; nor did Southwest have a known problem with employee use of alcohol or drugs. Nevertheless, Southwest decided to expand its drug policy. Specifically, it decided to implement a drug and alcohol testing program. The program is comprehensive and detailed. It prohibits detectable levels of illegal drugs, defined blood alcohol levels, and any level of medication that could impair performance, as well as any possession of illegal drugs. To enforce these prohibitions, the program mandates pre-employment urine drug screening, and urine drug screening of employees after accidents or if management has a reasonable suspicion of drug or alcohol use. The program establishes detailed testing procedures, and prescribes punishment, including discharge, for violations of the policy.
On October 16,1986, Southwest informed the Teamsters of its intention to implement the program. The Teamsters then sought to bargain over the terms of the program. Southwest was willing to discuss the program, but refused to negotiate with the Teamsters over it. Other unions did participate in discussions with Southwest, and these discussions affected the shape of the program.
*1132B.
In December 1986, the Teamsters filed this action, seeking to enjoin Southwest’s unilateral imposition of the program. In January 1987, the district court granted a preliminary injunction. The district court reasoned that the implementation of the program was not arguably justified under the terms of the collective bargaining agreement and that, therefore, the dispute was “major” and thus subject to bargaining before implementation. In the alternative, the district court held that even if the dispute were “minor,” a preliminary injunction was warranted by the likelihood of irreparable harm to employees if the program were enforced before the union’s objections to the program could be arbitrated.
Southwest appealed the preliminary injunction and it was affirmed. 842 F.2d 794. The panel concluded that the program was a mandatory subject of bargaining under the RLA that had not been clearly and unmistakably waived by the Teamsters in the management rights clause of the agreement. Next, the panel agreed with the district court that the dispute was “major” because it was not arguably justified by the management rights clause, Rule G, or past practices of the parties. As a major dispute, the matter was subject to bargaining and could not be unilaterally imposed by Southwest.
Sitting en banc, we disagree that the dispute is major; we thus reverse the district court and dissolve the injunction.
C.
We first note that this case continues to present a justiciable controversy. Although the agreement precipitating the suit has since terminated and a new one has been negotiated, the parties did not bargain about or agree upon a resolution to this dispute. The relevant terms of the new agreement track those of the old. Furthermore, Southwest adheres to its position that it is entitled to implement unilaterally its drug testing program, and has expressed its intention to do so should this court vacate the injunction. The union continues to object to the unilateral imposition of the program. The injunction has not expired of its own force.
Therefore, in deciding whether the injunction should stand, we need not avoid the merits of the suit by finding it moot. A case is not moot so long as “the prospect of repetition may affect continuing relationships in clear and tangible ways.” C. Wright, A. Miller, and E. Cooper, 13A Federal Practice and Procedure, § 3553.3 (2d ed.1984). Labor litigation, which presents both the problem of lapsed contracts and settled suits, has frequently required courts to determine whether such “clear and tangible” influence continues despite changes in the relation between the parties. In order to deal with this problem, there has arisen “a doctrine, apparently peculiar to labor questions, that governs the determination of mootness when parties agree on a new contract during the pendency of the suit.” Division 580 v. Central New York RTA, 578 F.2d 29, 32 (2d Cir.1978). The special treatment due labor questions has been recognized several times by the Supreme Court. See, e.g., Jacksonville Bulk Terminals, Inc. v. International Longshoremen’s Ass’n, 457 U.S. 702, 704 n. 1, 102 S.Ct. 2672, 2776 n. 1, 73 L.Ed.2d 327 (1982); Buffalo Forge Co. v. United Steelworkers of America, 428 U.S. 397, 403 n. 8, 96 S.Ct. 3141, 3146 n. 8, 49 L.Ed.2d 1022 (1976); Super Tire Engineering Co. v. McCorkle, 416 U.S. 115, 94 S.Ct. 1694, 40 L.Ed.2d 1 (1974). In Jacksonville Bulk Terminals, the Court adjudicated a dispute arising out of a work stoppage. The stoppage had been voluntarily abandoned six months before the Court heard argument, but the Court held the case jus-ticiable nonetheless. It commented, “[Tjhere remains a live controversy over whether the collective-bargaining agreement prohibits politically motivated work stoppages, and the Union may resume such a work stoppage at any time. As a result, this case is not moot.” 457 U.S. at 704 n. 1, 102 S.Ct. at 2676 n. 1. Similarly, the Court found a live controversy in Buffalo Forge despite the fact that the collective bargaining agreements in effect when the action arose had expired, where the parties *1133stipulated that those agreements governed the resolution of that dispute. 428 U.S. at 403 n. 8, 96 S.Ct. at 3146 n. 8. In the same way, the parties here, in effect, simply declined to settle this action when they negotiated a new agreement without resolving this dispute. Thus, our case is no less justiciable than Buffalo Forge or Jacksonville Bulk Terminals.
II
A.
The premise of the Teamsters’ request for an injunction begins with Southwest’s duty to bargain with the union before imposing terms of employment, including rates of pay, rules, and working conditions. 45 U.S.C. § 152, First, Second. Once bargaining has resulted in an agreement, however, not all disputes over changes in the terms of employment are subject to a continuing duty to negotiate. Rather, the RLA distinguishes the procedures for resolution of two different types of disputes that arise under a collective bargaining arrangement, which have come to be known as major and minor disputes. See Elgin, J. & E. Ry. Co. v. Burley, 325 U.S. 711, 722-28, 65 S.Ct. 1282, 1289-92, 89 L.Ed. 1886 (1945). “Major” and “minor” do not necessarily refer to important and unimportant disputes, or significant and insignificant issues; rather, the terms refer to the bargaining context in which a dispute arises. Major disputes involve proposals for new agreements or for changes in existing agreements. Id. at 723, 65 S.Ct. at 1289. Minor disputes, on the other hand, involve grievances over the application of an existing agreement. Id. This distinction matters because the RLA prescribes differing courses for the resolution of these two types of disputes. Major disputes go first to mediation; if not resolved, the parties may agree voluntarily to arbitrate, or the President may intervene, 45 U.S.C. § 155, First, § 160. During these steps parties must abide by the existing agreement; only if these steps fail may the parties resort to strikes or other self-help or, in the case of management, unilateral action. Burlington Northern R.R. Co. v. Brotherhood of Maintenance of Way Employees, 481 U.S. 429, 107 S.Ct. 1841, 1851, 95 L.Ed.2d 381; 45 U.S.C. §§ 155, 156, 160. Until these preliminary steps are exhausted, unilateral action can be enjoined. International Association of Machinists v. Frontier Airlines, Inc., 664 F.2d 538, 540-41 (5th Cir.1981).
Minor disputes are treated differently. If the parties do not agree on the interpretation or application of an agreement, the dispute is submitted to arbitration before an adjustment board. 45 U.S.C. § 153. Unlike its policy governing major disputes, the RLA does not prohibit unilateral action based on a party’s own interpretation of the agreement pending exhaustion of arbitration; only in a narrow set of cases may unilateral action be enjoined during resolution of a minor dispute. Frontier Airlines, 664 F.2d at 541. Thus, the propriety of the injunction imposed by the district court turns on whether the dispute over Southwest’s right under the agreement to implement the drug testing program unilaterally is a major or a minor dispute.
Case law has refined the test for whether a dispute is minor. Under Fifth Circuit precedent, a dispute is minor if the existing collective bargaining agreement affords some arguable basis for the underlying action. REA Express, Inc. v. Brotherhood of Railway, Airline and Steamship Clerks, 459 F.2d 226, 231 (5th Cir.1972) (quoting United Industrial Workers v. Board of Trustees, 351 F.2d 183, 188 (5th Cir.1965)). REA Express involved a claim by management that an agreement provided a procedure for altering truck runs. 459 F.2d at 230. According to the court, “[t]he key word in this test is ‘arguable.’ If the court finds an arguable basis it must defer to the expertise of the Adjustment Board.” Id. at 231. In a similar, earlier case, where a railroad based its right to abolish yardmaster positions on a clause (Rule 16(e)) providing that the agreement “shall not be construed as ... restricting the Company’s right to discontinue yardmaster positions,” this circuit reversed a lower court decision that the dis*1134pute was major. St. Louis, Santa Fe and Topeka Ry. Co. v. Railroad Yardmasters of America, 328 F.2d 749, 751, 754 (5th Cir.1964).
Unless we are to ignore completely the language of Rule 16(e) which on its face, according to the ordinary understanding of the English language does authorize the abolition of yardmaster positions, we are at a loss to understand how it could be decided that the rights of the union can be determined without a construction of the employment contract or agreement. We do not, of course, ... attempt to construe the contract. This is to be done by the appropriate tribunal. We do say that a defense based upon the language of Rule 16(e) raises a substantial issue as to the interpretation of the contract. It is not a fictitious or merely colorable issue. Before a tribunal can decide that the terminations at issue were not justified, it must construe the language of Rule 16(e).
Id. at 753.
Other cases have also applied this test to disputes over management’s right under an agreement to take certain actions. See, e.g., Railway Express Agency, Inc. v. Brotherhood of Railway, Airline and Steamship Clerks, 437 F.2d 388 (5th Cir.1971). In Railway Express Agency, the court described a dispute over a change in work assignment as follows:
The dispute in reality is over the breadth of management’s prerogative .... [Tjhere is no express provision allowing management to transfer the work unilaterally. However, the agreement does expressly reserve “the right of management to determine methods of operation and the utilization of the working forces.... ” Moreover, there is an undisputed history of such unilateral transfers of work with no apparent objection from the union. It may be concluded ... that this state of facts gave REA at least the arguable right to make the transfer.... Whether it actually has such a right must be determined by the Special Adjustment Board.
Id. at 392. In reaching this conclusion, the court in Railway Express Agency, id. at 393-94, relied heavily on Rutland Ry. Corp. v. Brotherhood of Locomotive Engineers, 307 F.2d 21 (2d Cir.1962). In Rut-land, the Second Circuit was faced with the question
whether the railroad has the unilateral right to make ... changes [in train schedules] without negotiating about them with the brotherhoods_ Whether it be a major or a minor dispute, the disagreement is a dispute over the scope of the railroad’s managerial prerogative. It is a major dispute if the present agreements between the railroad and the brotherhoods contain express provisions contrary to the position taken by the railroad or if the clear implication of these agreements is inconsistent with the railroad’s proposals. It is a minor dispute if there is a clearly governing provision in the present agreements, although its precise requirements are ambiguous; and it is also minor if what the railroad seeks to do is supported by customary and ordinary interpretations of the language of the agreements.
307 F.2d at 33-34 (citations omitted). The court there went on to hold that the dispute was minor even though no provision in the agreement explicitly granted the railroad the right to make the challenged changes unilaterally. Id. at 35-36 (citing cases where courts faced with similar disagreements classified the disputes as minor).
These cases clearly establish the rule that if the management’s underlying action is arguably justified by the collective bargaining agreement, the dispute is minor. Railway Express, 459 F.2d at 231. In other words, if management’s construction of the collective bargaining agreement and its unilateral action pursuant thereto create an issue that is not fictitious or merely colorable, then the issue should be resolved by the appropriate arbitration board. St. Louis, S.F. & T. Ry., 328 F.2d at 753.
B.
(1)
Although the district court recited and applied this standard, we cannot accept *1135its conclusion that this clause did not even arguably justify the program. On its face, this clause at least arguably grants management the right to enforce its policy by unilaterally promulgating rules, regulations, and orders such as this drug testing program. The clause provides:
Employees covered by this Agreement shall be governed by all Company rules, regulations and orders previously or hereafter issued by proper authorities of the Company which are not in conflict with the terms and conditions of this Agreement, and which have been made available to the employee prior to becoming effective.
In harmony with its provisions, the following facts cannot be denied: (1) the program consists of rules, regulations and orders within the meaning of this clause; (2) the program was issued by the proper authorities of the company; (3) no term or condition of the collective bargaining agreement conflicts with the program; (4) the program was made available to employees prior to becoming effective. Thus, Southwest seems to have complied fully with all conditions of the management rights clause to which the union had agreed. As a result, it is arguable that the program is a proper exercise of management’s rights. The merits of the interpretation of the agreement are clearly for the arbitrator to decide.
The panel opinion nevertheless states that this clause “does not speak at all to the right to bargain over rules, only the willingness to abide by rules validly enacted.” Although this may ultimately be the correct interpretation of the clause, we decline to say that the plausibility of such interpretation bars the contrary view that the clause binds employees to any and all rules that do not conflict with the agreement and that are promulgated by management with advance notice. Since the outcome thus turns on a choice between two arguable constructions, the dispute is minor, and must be submitted to arbitration.
This conclusion is further supported by the history of rule-making under the agreement. Southwest unilaterally promulgated Rule G, a rule establishing a drug and alcohol policy. Although Rule G has not required significant enforcement, its existence demonstrates a history under the agreement of unilaterally promulgating rules supporting a drug and alcohol policy. Thus, although the drug testing program is more extensive than Rule G, the unquestioned validity of Rule G, when considered in tandem with the management rights clause, indicates that the new program is arguably justified by the collective bargaining agreement.
(2)
The Teamsters argue further, however, that Southwest’s unilateral implementation of the program will infringe on the union’s statutory right to bargain. The panel held, and we agree, that the program effects a change in rules and working conditions and therefore is a mandatory subject of bargaining. Of course, the same is true of any new rule or order promulgated under the management rights clause that affects working conditions, however insignificant such rule might be. The panel also held, however, that Southwest had to bargain over the program because the management rights clause does not constitute a waiver of the union’s right to bargain about rules, regulations, and orders such as the drug testing program.
In general, the contractual waiver of a statutory right under federal labor law must be clear and unmistakably expressed. Metropolitan Edison Co. v. N.L.R.B., 460 U.S. 693, 707-08, 103 S.Ct. 1467, 1476-77, 75 L.Ed.2d 387 (1983). Metropolitan Edison concerned a no-strike clause, but this general rule of construction has been applied to questions of waiver of the duty to bargain. See, e.g., NL Industries, Inc. v. NLRB, 536 F.2d 786, 788-89 (8th Cir.1976); Pepsi-Cola Distributing Co., 241 N.L.R.B. 869 (1979); Ador Corp., 15 N.L.R.B. 1658 (1965); General Motors Corp., 149 N.L.R.B. 396, 399-400 (1964). All of these cases, however, arose under the National Labor Relations Act (“NLRA”). We are not certain that this rule of construction applies identically to the RLA. The rule operates to *1136protect rights defined by statute. Thus, we turn to the RLA to examine the nature of the bargaining right at issue here. The RLA, like the NLRA, does create a duty to bargain. Unlike the NLRA, however, the RLA distinguishes minor from major disputes and thereby defines within the statute the specific procedures governing the right to bargain, including the proper forum for resolving disputes over the extent of that right under an existing agreement. Thus, the statutory right to bargain created by the RLA, unlike that of the NLRA, is limited by the RLA’s precise regulation of procedures for dispute resolution. We note, furthermore, that none of this circuit’s cases involving contractual claims to management rights (see discussion above), discusses the issue in terms of a “clear and unmistakable waiver.” In fact, there appears to be a tension between deciding on the one hand whether a management rights clause arguably permits management to take some action, and deciding on the other hand whether such a clause clearly and unmistakably waives the right to bargain. Given the difference between the statutes, and given our prior cases, we find it to be a debatable matter of law whether, or to what extent, the rule of construction requiring that a waiver of bargaining rights under the NLRA be clear and unmistakable applies in a case arising under the RLA.
We find, however, that we are not squarely presented at this time with the question of how the “clear and unmistakable” rule applies to RLA cases. Even assuming, as the panel opinion assumes, that the management rights clause can give Southwest the right unilaterally to implement the program only if the clause is a clear and unmistakable waiver, the construction proposed by Southwest satisfies the minimal burden of arguably being a clear and unmistakable waiver. As noted above, the clause on its face binds employees, for the period of the agreement, to all rules, regulations, and orders that are issued by proper authorities, are not in conflict with other terms of the agreement, and are published in advance. Since there is no dispute that these conditions have been satisfied here, it seems clear that the drug testing program is a rule or regulation that falls within the terms of the management rights clause. Thus, there is an obvious argument that this clause constitutes a clear waiver of the union’s right to bargain over all rules, including the new drug rules. We reiterate, of course, that we are not actually deciding the applicability or scope of this clause. We decide only that the arbitration board is the forum authorized to construe the clause.
III
The district court held in the alternative that, even if the dispute is minor, an injunction is nevertheless warranted because of the potential harm of an improperly implemented drug testing program. We review this alternative holding under a deferential standard, and reverse only for abuse of discretion. Frontier Airlines, 664 F.2d at 542. We also note, however, that the proper grounds for granting an injunction against action that is the subject matter of a minor dispute under the RLA are extremely narrow. Id. at 541-42. Such injunctions may issue only where necessary to preserve the jurisdiction of the grievance procedure, or where a disruption of the status quo would result in irreparable injury of such magnitude that it would render any subsequent decision meaningless. Id. at 542. The district court found that irreparable harm to an employee’s reputation could result, for example, from disciplinary action taken against that employee or from an employee’s refusing to be tested under the program. Since many employment disputes involving discharge implicate the reputation of an employee, we do not believe that this speculative possibility of irreparable harm is of the magnitude required to support an injunction in the context of a minor dispute. Accordingly, we hold that it was an abuse of discretion to issue an injunction on the facts of this case.
IV
The drug testing program implemented by Southwest is arguably justified by the *1137management rights clause in the agreement. Thus, this dispute is minor, and the district court’s injunction pending the dispute’s resolution was improper. Accordingly, the injunction is
VACATED.*
Because of timing, Consolidated Rail Corp. v. Railway Labor Executives’ Ass’n, — U.S. -, 109 S.Ct. 2477, — L.Ed.2d - (1989), played no role in the consideration of this case by our en banc court. In Consolidated Rail, the Supreme Court held that the railway's inclusion of drug testing in periodically required physical examinations raised a minor dispute in that the action was arguably justified by implied terms of the parties’ agreement. There are significant differences between the facts of Consolidated Rail and our case, as well as distinct contractual bases for the respective decisions. We note only that the Supreme Court’s discussion of major and minor disputes supports our analysis and conclusion, and we see nothing in our opinion requiring modification on account of the Supreme Court’s decision in Consolidated Rail.