with whom Justice Brennan joins as to Parts I and II, dissenting.
The central question in this Railway Labor Act (RLA) case is whether it is unlawful for a carrier to refuse to reinstate employees who supported a strike until its end (“full-term strikers”) solely because the carrier chooses to retain in its active work force employees who returned to work before the strike’s conclusion (“crossovers”).1
The Court today answers that question in the negative, concluding that such conduct never violates the RLA, regardless of whether business necessity dictated the carrier’s course of action. In dissent, Justice Brennan takes the diametrically opposite view, in agreement with the Court of Appeals. Justice Brennan finds such conduct “inherently destructive,” ante, at 443, of the right to strike and violative of the RLA regardless of any proffered business justification. In my view, neither of these positions accurately captures the delicate balance our RLA precedents have attempted to achieve between the public’s dual interests in the maintenance of transportation service during labor disputes and in the long-term stability of labor relations in the rail and airline industries.
*453My differences with Justice Brennan are limited in scope. Concisely stated, I give greater weight than he does to the RLA’s policy in favor of continued operations, and accordingly conclude that this case should be remanded to permit TWA to make a factual showing that its crossover policy truly was necessary for that purpose. The Court’s opinion presents far greater concerns, as much because of the false' assumptions that underlie the Court’s analysis as because of its erroneous result.
I
The threshold question is whether the provisions and policies of the RLA place any limit on a carrier’s exercise of self-help during a strike. The Court acknowledges that the RLA does contemplate such a limit. Indeed, there would be little need to distinguish, see ante, at 436, TWA’s crossover policy from the superseniority policy in NLRB v. Erie Resistor Corp., 373 U. S. 221 (1963), if the RLA had no relevance to the legality of grants of superseniority, or to other, even more egregious, discriminatory, and coercive employer practices. But the Court adopts a stingy interpretation of the RLA, reserving the RLA’s protective force for only the most extraordinary circumstances. In so doing, the Court uses language which suggests that any limit on employer self-help must be “implied],” ante, at 442, which in turn suggests that the Court finds no express limit in the text of the RLA. I find no basis for that view, a view which does not sit comfortably with the Court’s opinion read as a whole and which results in a far too restrictive reading of the RLA.
When the Court addressed the permissible scope of employer self-help under the RLA in Trainmen v. Jacksonville Terminal Co., 394 U. S. 369 (1969), it held that the RLA permits “parties who have unsuccessfully exhausted the-Railway Labor Act’s procedures for resolution! of a major dispute to employ the full range of whatever peaceful economic power they can muster, so long as its use conflicts ivith no- other obligation imposed by federal law Id., at 392 (emphasis *454added). In applying that holding to the facts of this case, the Court rejects the proposition that § 2 Fourth of the RLA, 44 Stat. 577, as amended, 45 U. S. C. § 152 Fourth, creates a relevant conflicting federal obligation.
The Court’s stated reason for rejecting the applicability of § 2 Fourth sweeps too broadly. The Court places great emphasis on the fact that the 1934 amendments which introduced §2 Fourth had a “precertification focus.” Ante, at 441. It should be clear, however, that a precertiflcation focus is not the same as a postcertification blindspot. In 1934, Congress was faced with evidence that railroad employees’ efforts at self-organization had been thwarted by coercive employer tactics, including the support of employer-dominated company unions. See Machinists v. Street, 367 U. S. 740, 759 (1961). Certainly, Congress had cause for concern: unless each side is free to choose its own bargaining representative, there can be no legitimate bargaining relationship. There is no indication, however, that Congress’ concern in enacting § 2 Fourth is satisfied at the moment of a union’s certification. Congress aimed to protect the employee’s right to organize and join unions “with a view to asserting himself as to hours, conditions, and wages,” 78 Cong. Ree. 11720 (1934) (remarks of Rep. Monaghan) — not as an end in itself. This Court long has recognized that a “primary purpose of the major revisions made in 1934 was to strengthen the position of the labor organizations vis-a-vis the carriers, to the end of furthering the success of the basic congressional policy of self-adjustment of the industry’s labor problems.” Machinists v. Street, 367 U. S., at 759.
Indeed, the Court today acknowledges that, precertification focus notwithstanding, §2 Fourth has relevance to the right of employees to decide whether to assist in postcerti-fication union activities, free from employer coercion. The Court places substantial reliance on § 2 Fourth as the source of “an employee’s right to choose not to strike,” ante, at 436, *455a right relevant to this case only if it applies to posicertification strike activity.
Finding § 2 Fourth to be a source of the right not to strike is entirely proper. In Radio Officers v. NLRB, 347 U. S. 17 (1954), the Court held that the protection § 8(a)(3) of the NLRA affords against employer discrimination “to . . . discourage membership in any labor organization,” 29 U. S. C. § 158(a)(3), extends to “discrimination to discourage participation in union activities as well as to discourage adhesion to union membership.” 347 U. S., at 40. I see no reason why similar language in §2 Fourth, i. e., its protection of employees’ right to “join or remain or not to join or remain members of any labor organization,” should not be read in a similar fashion. Cf. Trainmen v. Jacksonville Terminal Co., 394 U. S., at 385, n. 20. Neither, apparently, does the Court. And if §2 Fourth bars discrimination or retaliation against employees who choose not to strike, the same must be true of discrimination or retaliation against employees who choose to strike. See Railway Labor Executives’ Assn. v. Boston & Maine Corp., 808 F. 2d 150, 158 (CA1 1986), cert. denied, 484 U. S. 830 (1987); Air Line Pilots Assn. v. United Air Lines, Inc., 802 F. 2d 886, 897 (CA7 1986), cert. denied, 480 U. S. 946 (1987).
In contrast, the Court’s suggestion that the RLA provides employees no express protection against discrimination on the basis of levels of support for union activities leads the Court to limit the RLA’s force to whatever protections this Court is willing to “imply” from the RLA’s general policies. This uncertainty carries with it the danger of undermining the stability of labor relations under the RLA. Under this Court’s longstanding RLA jurisprudence, a strike that takes place after the RLA’s dispute resolution mechanisms have failed “represents only an interruption in the continuity of the relation” between employer and union, not an invitation for “labor-management relations [to] revert to the jungle.” Railway Clerks v. Florida East Coast R. Co., 384 U. S. 238, *456246-247 (1966). Stated otherwise, a strike under the RLA is a “bounded conflict.” Cf. Estreicher, Strikers and Replacements, 38 Lab. L. J. 287, 288 (1987). Contract negotiations are limited in scope to the matters raised by the parties’ bargaining notices, see 45 U. S. C. § 156; both during and after strikes that occur following unsuccessful mediation, the union often will maintain its status as exclusive bargaining representative. See, e. g., Trans World Airlines, Inc. v. Independent Federation of Flight Attendants, 809 F. 2d 483, 492 (CA8 1987), aff’d by equally divided Court, 485 U. S. 175 (1988). The long-term stability of labor relations thus will depend upon the maintenance of the working relationship between the union and the employer. This Court has been aware in the past that one party’s power of self-help cannot be permitted effectively to negate the other’s, lest “the right of self-help . . . become unilateral,” Railway Clerks v. Florida East Coast R. Co., 384 U. S. at 246, and that a carrier cannot be permitted to reap rewards from a strike so much in excess of the rewards of negotiation that it will “have a strong reason to prolong the strike and even break the union.” Id., at 247. The central emphasis of the RLA on continuity of labor relations requires courts to take the long view. See, e. g., Empresa Ecuatoriana de Aviacion v. District Lodge No. 100, 690 F. 2d 838, 845 (CA11 1982), cert. dism’d, 463 U. S. 1250 (1983); National Airlines, Inc. v. International Assn. of Machinists & Aerospace Workers, 416 F. 2d 998, 1006 (CA5 1969).
The Court’s position leaves far too little room for these concerns. By interpreting the RLA as affording protection to striking employees only in the most unusual circumstances, the Court encourages employers to test the limits, knowing that the burden will fall on the employees to demonstrate that the employer’s conduct has crossed an artificially high barrier of “implied” tolerance for employer coercion. The Court thus needlessly creates incentives to undermine long-*457term labor stability and to expand labor conflicts beyond their natural bounds.
In sum, this Court consistently has recognized that there is a difference between traditional self-help economic pressure and coercion or discrimination in derogation of federal law. The Court today continues to recognize this principle, and is willing to “imply” protection in extraordinary circumstances. But Congress did not leave the protection of employee rights to this Court’s selective “implication.” I reject this Court’s failure to give full force to §2 Fourth, the RLA’s express statutory prohibition of coercive and discriminatory employer conduct.
II
Even under the standards the Court articulates today, the result it reaches in this case cannot stand. The Court’s conclusion that TWA’s conduct cannot be said to violate the statutory rights (implied or otherwise) of full-term strikers fails to take seriously the significant discriminatory impact of TWA’s refusal to reinstate full-term strikers. That failure rests on two assumptions that are patently inconsistent with central tenets of federal labor law.
First, the Court appears to suggest that because there were no “vacancies” for the full-term strikers to fill, employer “discrimination” cannot have been a factor in the final allocation of poststrike positions in the active work force. Contrary to this view, this Court long has held that the mere fact that a particular employee occupies a job at the conclusion of a strike does not entitle the employee to retain that job. This is illustrated by our NLRA precedents. Under NLRB v. Mackay Radio & Telegraph Co., 304 U. S. 333, 347 (1938), an employer subject to the NLRA is “not bound to displace men hired to take the strikers’ places in order to provide positions for them” if the employer has found it necessary to promise the replacements permanent employment in *458order to operate during the strike.2 In contrast, positions occupied by new hires to whom no promise of “permanent replacement” status is made are as good as “vacancies” from the full-term strikers’ point of view. The employer’s legal right to resist a union demand for reinstatement flows from the necessity of the offer of permanence; absent such necessity, the employer may be required to furlough (or discharge) the replacements to make room for the strikers’ return. See NLRB v. Fleetwood Trailer Co., 389 U. S. 375, 378-379 (1967); Belknap, Inc. v. Hale, 463 U. S. 491, 514, 517 (1983) (opinion concurring in judgment). The poststrike situation is not, in short, a game of musical chairs: it is governed not by the rule of capture, but by conflicting claims of legal entitlement.
Second, and in tacit recognition that the poststrike situation is governed by law rather than by force or happenstance, the Court elevates the rights of crossovers to the preeminent position, a position which in the Court’s view flows naturally from the RLA’s and NLRA’s protection of “an employee’s right to choose not to strike.” Ante, at 436. From the fact that some employees will disagree with the union’s decision to strike, the Court deduces the proposition that “employees who chose not to gamble on the success of the strike” should not “suffer the consequences when the gamble proves unsuccessful.” Ante, at 438.
The Court’s analysis entirely ignores, and threatens to vitiate, the “‘majority-rule concept [that] is today unquestionably at the center of our federal labor policy.’” NLRB v. Allis-Chalmers Mfg. Co., 388 U. S. 175, 180 (1967), quoting Wellington, Union Democracy and Fair Representation: Federal Responsibility in a Federal System, 67 Yale L. J. 1327, 1333 (1958). “Congress has seen fit to clothe the bargaining representative with powers comparable to those possessed *459by a legislative body both to create and restrict the rights of those whom it represents.” Steele v. Louisville & Nashville R. Co., 323 U. S. 192, 202 (1944) (discussing the duty of fair representation). What the Court characterizes as “their union’s decision to strike,” ante, at 437 (emphasis added), is the decision reached by the majority of the members of the bargaining unit through democratic processes. The right to remain a member of the collectivity but to opt out of the consequences of particular collective decisions when the going gets rough is not a normal incident of participation in the democratic process.
The Court also overlooks the long-recognized fact that the benefits of successful union activity flow to all members of the bargaining unit regardless of their personal support for the union. See Railway Employees v. Hanson, 351 U. S. 225, 238 (1956); Machinists v. Street, 367 U. S., at 762. By elevating the right of crossovers to be “free rider[s],” id.., at 762-763, nn. 13 and 14, to the status of a first principle of labor law, the Court forgets that, by definition, the benefits and burdens of collective action are borne collectively.
This newly asserted statutory right of dissidents to be free from the consequences of collective action buckles under the heavy load the Court asks it to bear. As TWA concedes and the Court recognizes, employers and unions often lawfully agree to displace crossovers through poststrike back-to-work agreements, and employers may unilaterally decide to permit such displacement. See Brief for Petitioner 29; see also Copaz Packing Corp., 115 LRRM 1008, 1008 (1983) (NLRB General Counsel Advice Memorandum) (employers are “privileged to enter into a strike settlement which providefs] that . . . crossovers and strikers who remained on strike until the settlement would be treated equally for recall purposes”); Florida East Coast R. Co., 41 Lab. Arb. 1001, 1006-1007 (1963) (recommendation of Presidential Emergency Board that the carrier replace crossovers and new-hire replacements, who were the poststrike “occupants of the jobs cov*460ered by agreements between the Carrier and the organizations with striking employees to the extent necessary to permit these jobs to be filled on the basis of seniority”). If the right of dissidents to be free of the economic consequences of strikes is so central, it is difficult to see why the union has the power to bargain it away or why the employer has the power to ignore it.
In sum, the Court concludes that TWA’s conduct was lawful on the basis of two assumptions: that the resulting job distribution is justified by the absence of “vacancies” for the returning strikers, and that TWA’s acts were a necessary consequence of its duty to respect the crossovers’ statutory right not to strike. The Court allows these assumptions to stand in the way of considering the adverse impact of TWA’s actions on the full-term strikers’ statutory rights. But I find these assumptions to be without foundation, and thus turn to the question the Court fails to reach.
l — t h — I I — I
A
At the conclusion of the strike, TWA refused to reinstate full-term strikers to positions then occupied by crossovers. In analyzing the lawfulness of TWA’s conduct, certain NLRA principles provide a useful starting point. This Court has recognized under the NLRA that an employer’s refusal to reinstate striking employees discourages employees from exercising their right to organize and to strike, NLRB v. Fleetwood Trailer Co., 389 U. S., at 378, and violates the statutory prohibition against discrimination “unless the employer . . . can show that his action was due to ‘legitimate and substantial business justifications.’” Ibid., quoting NLRB v. Great Dane Trailers, Inc., 388 U. S. 26, 34 (1967). If the employer fails to meet this burden, the inquiry is at an end. Furthermore, in certain circumstances, “the Board can find an unfair labor practice even if the employer introduces evidence that the conduct was motivated by business consider*461ations,” id., at 34, by striking “‘the proper balance between the asserted business justifications and the invasion of employee rights.’” Metropolitan Edison Co. v. NLRB, 460 U. S. 693, 703 (1983), quoting Great Dane, 388 U. S., at 33-34.3
These basic principles are consistent with our RLA precedents. In Railway Clerks v. Florida East Coast R. Co., 384 U. S. 238 (1966), the carrier, during a strike, resorted to self-help in facial violation of § 2 Seventh of the RLA, which prohibits unilateral changes in terms and conditions of employment embodied in collective agreements. The Court held that the carrier could not fulfill its duty to the public to make reasonable efforts to maintain service during the strike if § 2 Seventh were applied with full force during strikes. To accommodate the public interest in continued service, it inter*462preted the RLA as granting the carrier a “closely confined and supervised” power to alter the terms of the agreement during a strike in order to continue service under the particular strike conditions presented by that case. 384 U. S., at 246. The appropriate standard for reviewing a carrier’s alteration of an agreement, the Court concluded, was adequately captured by the words “reasonably necessary,” “provided that ‘reasonably necessary’ is construed strictly” to mean “only such changes as are truly necessary ... for the continued operation” of the carrier. Id., at 248.
In this case, we address conduct that facially violates a different provision of the RLA: § 2 Fourth’s bar against conduct by a carrier which, by its natural tendency, induces or influences employees in their decisions to support or refrain from supporting union activities. The logic of Florida East Coast R. Co., however, is equally applicable here and suggests that a carrier’s refusal to reinstate strikers — conduct which, on its face, violates § 2 Fourth because of its tendency to influence adversely employees’ willingness to support strikes — is unlawful if the refusal was not truly necessary for the continued operation of the carrier during the strike.
In my view, there is no basis under the RLA for a presumption that offers of permanence are necessary in order to induce crossovers and outside replacements to work during a strike. Cf. Hot Shoppes, Inc., 146 N. L. R. B. 802, 805 (1964); Belknap, Inc. v. Hale, 463 U. S., at 504, n. 8 (discussing presumptive necessity of offers of permanence to outside replacements under the NLRA). The Court recognized in Florida East Coast R. Co., 384 U. S., at 246, that a carrier may have need to “improvis[e] and emplo[y] an emergency labor force” in order to continue operations. Under the RLA, as under the NLRA, in short, the Court has recognized that the employer has “the right to protect and continue his business by supplying places left vacant by strikers.” NLRB v. Mackay Radio & Telegraph Co., 304 U. S., at 345. The Union does not here dispute that proposition, *463nor does it question that RLA employers may offer new hires “permanent” status. Cf. id.., at 346. But this Court has also recognized that the public has an interest in the long-term stability of labor relations in industries governed by the RLA. See Virginian R. Co. v. Railway Employees, 300 U. S. 515, 552 (1937). A rule that presumes that replacements and crossovers must be offered permanence would needlessly infringe on that interest in stability.
“There may be some who will. . . argu[e] that employees must take their chances on being permanently replaced when they elect to go on strike. There is little doubt that striking employees have lost their jobs in many firms through the application of this principle. On the other hand, we are concerned in this case not with an ordinary private business but with a common carrier in an industry vital to the public. . . . Experience suggests that the prospects for achieving a ‘peaceable settlement’ of this dispute will remain in jeopardy so long as the striking employees are prevented from working by the presence of the newly-hired replacements. While this situation persists, the organizations can be expected to employ every legitimate means to put pressure on the company to reinstate the strikers. Controversy of this kind may interfere with the legitimate needs of passengers and shippers .... Moreover, other railroads may be tempted to follow the example of this carrier, thus provoking bitter and disruptive disputes in other sections of the country.” Florida East Coast R. Co., 41 Lab. Arb., at 1006-1007.
This risk should be taken only if absolutely necessary to the carrier’s continued operations. Presuming the need does gratuitous damage to significant statutory interests.4
*464B
In his dissent, Justice Brennan does not reach the question whether a carrier who offers permanence to replacements and crossovers is entitled to a presumption of business necessity. Indeed, he would not even permit TWA to make a case-specific showing that its crossover policy was necessary for its continued operation during the strike. Here, our positions differ: I would require the carrier to prove the business necessity of offering permanence to replacements and crossovers on the facts of each case.5
*465Justice Brennan rests his contrary position on NLRB v. Erie Resistor Corp., 373 U. S. 221 (1963). In that case, an employer granted 20 years’ superseniority to employees (new hires and crossovers) who had worked during a strike, which later placed reinstated full-term strikers at a substantial and long-term risk of layoff. There, the NLRB found, and this Court agreed, that “the employer’s insistence that its overriding purpose in granting super-seniority was to keep its plant open and that business necessity justified its conduct was unacceptable since ‘to excuse such conduct would greatly diminish, if not destroy, the right to strike guaranteed by the Act.’” Id., at 225-226 (quoting Erie Resistor Corp., 132 N. L. R. B. 621, 630 (1961)). Because the Court concluded that the stated business justification would not outweigh the asserted interest in continued operation, no factual inquiry into whether the employer’s claim that he could not otherwise have operated during the strike was held to be necessary.
Two considerations cause me to part ways with Justice Brennan’s conclusion. First, it is not so clear to me as it is to Justice Brennan, ante at 449, that TWA’s conduct in this case is sufficiently egregious for its destructive impact to outweigh the interest in maintaining operations during the strike. In Erie Resistor, this Court identified a number of factors that made grants of superseniority particularly harmful to employee rights. Several, but not all, of those factors are present in this case. TWA’s conduct, like the conduct at issue in Erie Resistor, induces employees to abandon the strike and particularly harms full-term strikers. See 373 U. S., at 230-231. But in Erie Resistor the Court stressed the fact that, for years after the strike, reinstated strikers would face a greater risk of layoff because of the additional seniority given to those who worked during the strike. Although Erie Resistor does not suggest an overarching principle identifying which factors are dispositive, the absence of a *466similar continued threat of loss of employment suggests to me that the crossover policy at issue here is not so destructive of employee rights as was the superseniority policy at issue in Erie Resistor. The fact that the Court struck the balance against the employer in Erie Resistor is thus not dis-positive of this case.
Second, and more generally, I am concerned that a standard that permits courts to balance employer and employee interests in the abstract, without a concrete evidentiary record, will lead to erroneous results that endanger the unique statutory interests embodied in the RLA. In the past we have recognized that the public has a significant interest in the continuity of transportation services during labor disputes, and that the RLA protects that interest. Railroad and airline industry employers, we have held, must make “reasonable efforts to maintain the public service at all times, even when beset by labor-management controversies.” Florida East Coast R. Co., 384 U. S., at 245. I recognize that we have stopped short of holding that federal law imposes an absolute duty to operate during strikes, see id., at 250 (White, J., dissenting), and thus have never held that the interest in continued operation cannot be outweighed by other concerns. In my view, however, the balance should be struck on a case-by-case basis and upon a factual record. I expect that it will be a rare case in which gravely destructive carrier conduct will be proved necessary to continued operation under the strict standard of necessity established by Florida East Coast. The ultimate question as to which interest should prevail in such a case is one we can afford to leave unanswered until it is presented on proper facts.
IV
Because the Court of Appeals found TWA’s conduct unlawful without considering whether TWA’s crossover policy was “truly necessary” for continued operations during the strike, I would vacate the judgment of the Court of Appeals and di*467rect that court to remand the case for consideration of that issue.6 Inasmuch as this Court is now reversing outright, I dissent.
The question has been presented by the parties, and is stated by the Court, in terms of reinstatement of full-term strikers with greater seniority. For i'easons explained in n. 6, infra, however, the question whether the final allocation of positions must be made on the basis of seniority is essentially remedial in nature. Cf. Lone Star Industries, Inc., 279 N. L. R. B. 550 (1986) (employer is free to choose any nondiscriminatory means of making its poststrike reinstatement decisions). The question upon which liability turns is whether the basis of the allocation made (i. e., the duration of the employee’s support for the strike) was discriminatory.
The employer, of course, may agree to discharge permanent replacements, subject to any claims the replacements may have under state law. See Belknap, Inc. v. Hale, 463 U. S. 491, 496-497, 500 (1983).
Under § 8(a)(3) of the NLRA, 29 U. S. C. § 158(a)(3), the employer’s motive is relevant to the analysis. See Metropolitan Edison Co. v. NLRB, 460 U. S. 693, 700 (1983); see generally Christensen & Svanoe, Motive and Intent in the Commission of Unfair Labor Practices: The Supreme Court and the Fictive Formality, 77 Yale L. J. 1269 (1968). The motive inquiry does not arise, however, unless the employer is able to demonstrate business justification for his actions. At that point, the course of the inquiry varies depending upon the severity of the adverse impact of the employer’s conduct on employee rights. Where the impact is relatively slight, the employer’s conduct will be deemed lawful unless the union proves that the employer’s conduct was motivated by antiunion animus. See NLRB v. Great Dane Trailers, Inc., 388 U. S., at 34. Where, in contrast, the impact is sufficiently severe to render the employer’s conduct “‘inherently destructive’ of important employee rights,” ibid., antiunion motive may be inferred from the conduct itself. See NLRB v. Erie Resistor Corp., 373 U. S. 221, 228, 231 (1963).
To decide this case, it is not necessary to resolve the question whether antiunion motive is a necessary element of a § 2 Fourth violation. I think it clear that the crossover policy at issue here is “inherently destructive” of employee rights: it is sufficiently destructive not to require an express showing of antiunion motive even under the motive-based standards of § 8(a)(3). For this same reason, I note, TWA’s conduct falls afoul of the RLA under the “inherently destructive” standard set forth by the Court in this case. See ante, at 442.
Count 2 of the union’s complaint seeks “to establish that it was not necessary for TWA to offer permanent jobs to the replacements hired from outside the pre-strike workforce and that TWA therefore violated the RLA by doing so.” Brief for Respondent 3, n. 5; see App. to Pet. for *464Cert. 55a-56a. That claim has not yet been tried and remains pending. See Tr. of Oral Arg. 42. The union has explained that Count 2 of the complaint, as drafted, proceeds on the theory that the employer is entitled to a rebuttable presumption that an offer of permanence is necessary for continued operation. Brief for Respondent 39. The union takes the position that although “there may well be a basis for erecting a presumption that offers of permanence to outside replacements are 'truly necessary’ in order to operate during a strike and placing the burden to prove otherwise on the injured full-term strikers or their union, there is no basis for any such presumption with regard to crossovers.” Ibid, (footnote omitted). I agree with the union that there is less basis for presuming the necessity of an offer of permanence in the case of crossovers than in the case of outside replacements. But, as indicated in the text, I would go further: I see no need to afford the carrier the benefit of a rebuttable presumption of business necessity even in the case of outside replacements.
Adopting a uniform standard applicable to both outside replacements and crossovers disposes of the argument that to permit full-term strikers to displace crossovers would have the anomalous result of treating crossovers more harshly than permanent replacements. Ante, at 434, 436; see Tr. of Oral Arg. 43. In a particular case, members of the prestrike work force may well return to work solely because they can no longer endure the present economic costs of the strike, and will do so without further inducement. If the carrier also needs to hire outside replacements, and legitimately finds that it can do so only by promising them that they will not be laid off to make room for returning strikers, the result in that case will be that the crossovers will have less protection from layoff than will the new hires. This result is not anomalous, however; it is merely the result of applying a uniform standard to disparate facts.
If it proved to be the case on remand that TWA’s crossover policy was indeed unlawful, the question (noted at n. 1, supra) would arise whether the union is entitled to the specific relief it seeks: the allocation of positions in the active work force on the basis of seniority. This Court suggested in NLRB v. Mackay Radio & Telegraph Co., 304 U. S. 333, 347 (1938), and the NLRB held in Lone Star Industries, 279 N. L. R. B. 550 (1986), that an employer may make its poststrike reinstatement decisions on the basis of any nondiscriminatory criterion. Because “[i]t is universally recognized, as a matter of sound labor relations, that seniority provides the employee with an equitable interest in continued employment,” Florida East Coast R. Co. 41 Lab. Arb. 1001, 1006 (1963), seniority is likely to be the neutral criterion of choice. Indeed, TWA unilaterally implemented a settlement proposal calling for reinstatement of full-term strikers to “vacancies” in seniority order. See App. 90-91; App. to Pet. for Cert. 52a-53a (Complaint "128).
Although this unilateral undertaking may well bind TWA at the remedial stage of this litigation, I note that the union has not based its entitlement to seniority-based relief on that ground. Nor has the union argued (at least explicitly) that specific provisions of its collective-bargaining agreement require that result. Cf. Eastern Air Lines, Inc., 48 Lab. Arb. 1005 (1967) (interpreting general seniority provisions of collective-bargaining agreement as applicable to poststrike reinstatement). Rather, the union’s argument for a seniority-based remedy appears to be purely statutory in nature. There is some merit to the view that the bounded nature of strikes under the RLA requires that seniority be used as the mechanism for poststrike reinstatement because it will achieve the closest possible approximation of the prestrike work force. But there is some danger that imposing seniority-based reinstatement as a statutory matter would place courts in the position of expanding contractual seniority provisions beyond their contemplated scope. In light of the likelihood that TWA would voluntarily employ seniority as a basis for its reinstatement decisions on remand, this question need not be reached.