The only issue we discuss in this case is whether, in sustaining the decision of the Federal Aviation Administration (Administration) removing the petitioner from his position as an air traffic controller for participating in the illegal air traffic controllers strike in August 1981, the Merit Systems Protection Board (Board) correctly rejected the petitioner’s argument that his absence from work resulted not from his participation in the strike but from his having been on annual leave. We vacate the Board’s decision and remand for further proceedings consistent with this opinion.
I
The facts relating to the nationwide air traffic controllers strike are set forth in our opinion in Schapansky v. Department of Transportation, 735 F.2d 477 decided today. A strike called by the Professional Air Traffic Controllers Organization (“PATCO”) began at 7 a.m. on August 3, 1981. At 11 a.m. on that date the President announced that the strike was illegal and that any striking controller who had not returned to work by 11 a.m. on August 5 would be discharged.
Letenyei had been authorized annual leave from August 2 through August 15, 1981. On August 1, 1981, the day before his annual leave was scheduled to begin, Letenyei’s supervisor notified him by telephone that his leave had been cancelled, effective 3:18 p.m. on August 3, 1981. Le-tenyei did not report for work on August 3 or 4, or for his shift on August 5 following *530the expiration of the Presidential deadline. On August 6, 1981, the Administration sent petitioner a written notice of proposed removal for striking and for being absent without leave beginning on August 3, 1981. Because Letenyei had moved, he did not receive the notice until August 20, 1981.
On August 15, 1981, the day before his previously scheduled leave had been due to expire, Letenyei called the agency to ascertain the shift on which he was scheduled to work on the following day. The agency told him not to report for work but to call two days later to arrange for an oral hearing.
On August 28, 1981, Letenyei made his oral response to the notice of proposed removal. He told the oral reply officer that he had made arrangements to move and to sell his house and then to go on vacation during his scheduled leave; that when he was informed on August 1 that his leave was cancelled, he was in the midst of moving and had a loaded truck at his house; that at that time “my priority was to take care of the houses and I could not change vacation plans”; and that “[ojwning two houses at the time and with moving and preparing both houses, it was just that I could not change plans or it would cost thousands within a week.” At the subsequent hearing before the Board, Letenyei also contended that the collective bargaining agreement between PATCO and the Administration precluded the agency from cancelling his leave.
After considering the oral reply, the Administration removed Letenyei for participation in the strike and absence without leave as charged. Letenyei appealed his removal to the Board.
A hearing was held before the presiding official of the Board’s regional office. The presiding official reversed the Administration’s removal of Letenyei from his position. She held that under the collective bargaining agreement the agency had no authority to cancel Letenyei’s leave. She further found that “there is no evidence that [Letenyei’s] refusal to [provide services to his employer] was in concert with others____ Rather, at all times since his leave was cancelled, [he] had insisted that the leave cancellation was improper, in violation of the union contract, and unacceptable to him because of his moving and vacation plans.” Kays v. Department of Transportation, Nos. CH075281F2014, CH075281F2202, slip op. at 5 (M.S.P.B.Phil. Reg’l Off. Nov. 22, 1982) (emphasis in original).
The presiding official held that Letenyei “was indeed AWOL on August 3-6, 1981 as charged by the agency.” Id. at 7. She based this conclusion upon his failure to obey the agency’s order to report for work on August 3, 1981. Although she held that order was improper, she further held that the petitioner was obligated to obey it and to depend upon the grievance procedure in the collective bargaining contract for redress. She ruled, however, “that removal for this AWOL offense is excessive,” id. at 8, and ordered the agency “to substitute a 60 day suspension” as the penalty. Id. at 12.
On the agency’s appeal, the Board reversed and reinstated the Administration’s removal action. The Board held that the collective bargaining agreement did not preclude the agency from cancelling Leten-yei’s leave. Kays v. Department of Transportation, Nos. CH075281F2014, CH075281F2202, slip op. at 4 (M.S.P.B. Apr. 25, 1983). Noting that Letenyei had “appealed at the picket line] at various times during the strike, and ... attended a PATCO rally on August 5, 1981,” id. at 5, the Board concluded that Letenyei “has failed to rebut the agency’s prima facie case in support of the charge of his participation in the PATCO strike____” Id. at 6.
II
A. Letenyei contends that the collective bargaining agreement between PATCO and the Administration barred the agency from cancelling his leave. He relies upon section 1 of article 28 of the agreement which, after specifying that each eligible employee was entitled to at least three consecutive *531weeks of annual leave for vacation, provided that
[t]his leave shall not be cancelled or rescheduled except for an operational emergency, or at the request of the employee.
He argues that this language authorized the Administration to cancel leave only when an operational emergency actually existed, but not in anticipation of one. Since the strike had not begun when the Administration cancelled his leave on August 1, 1981, Letenyei contends that the agreement precluded cancellation on that day. From these premises he apparently reasons that he still was on annual leave during the period the Administration found he was on strike (August 3-6) and that the strike finding therefore falls.
As noted, the presiding official adopted this interpretation of the agreement. She concluded that “a contract violation occurred when appellant’s leave was can-celled.” Kays, slip op. at 6 (Phil.Reg’l Off.).
In holding that the contract did not bar the cancellation of Letenyei’s leave, the Board relied upon its earlier decision in McPartland v. Department of Transportation, No. DA075281F1018 (M.S.P.B. Feb. 8, 1983), which it described as holding that this contract provision
requires only the existence or reasonable likelihood of the existence of an operational emergency before steps may be taken to cancel approved leave prospectively or actually to cancel such leave during the duration of the emergency. In this case, an operational emergency clearly existed as a result of the job action beginning on August 3, 1981.
The Board then ruled:
Further, the possibility of the occurrence of such an operational emergency was reasonably foreseeable on August 1, when the agency cancelled appellant’s leave____
... the agency’s prospective cancellation of appellant’s annual leave in anticipation of the imminent and reasonably foreseeable operational emergency was proper, and did not constitute a violation of the applicable PATCO-FAA bargaining agreement. Such leave was effectively cancelled so that appellant’s absence beginning on August 3, 1981, was unauthorized.
Kays, slip op. at 4-5 (M.S.P.B.) (footnotes omitted).
We agree with the Board’s interpretation of the agreement. Although article 28 recognized the importance of giving controllers annual vacation leave, it further recognized that the Administration must be able to cancel leave when “an operational emergency” required it. The threat of an imminent national strike by the air traffic, controllers fully justified, indeed required, the agency to cancel Letenyei’s leave so that he would be available to work during the strike. August 1, the day on which the agency cancelled his leave, was,' as the Board pointed out, only two days before the day on which the national president of PATCO had announced that the strike would begin.
This leave-cancelling provision obviously was designed to enable the agency to keep controllers on the job to deal with operational emergencies that might arise. Le-tenyei’s interpretation of the contract— that it permitted the Administration to cancel his leave only after the strike had begun, but not when the strike was imminent — is inconsistent with the basic purpose of the provision of giving the agency sufficient flexibility with respect to cancel-ling leave to enable it to deal effectively with emergency operational situations.
The amicus curiae points out that in holding in Giesler v. Department of Transportation, 3 M.S.P.B. 367 (1980), aff'd, 686 F.2d 844 (10th Cir.1982), that the Board would treat provisions of a collective bargaining agreement the same as it treats agency regulations, the Board described the collective bargaining agreement there as having “established nondiscretionary policy under which the [agency] operates.” 3 M.S.P.B. at 368. The amicus curiae argues that since the decision of the Adminis*532tration to cancel Letenyei’s leave was discretionary, the Board treated the collective bargaining agreement here differently than it treated such agreement in Giesler.
The “nondiscretionary policy” reflected in the PATCO agreement, however, was the basic concept that leave would not be cancelled except for “an operational emergency.” The determination whether such an emergency existed was for the Agency to make initially, and the making of that determination necessarily involved the exercise of the Agency’s discretion. Giesler cannot be read as barring the agency from cancelling Letenyei’s leave two days before the PATCO strike began.
B. Participation in a strike has been defined authoritatively as “an actual refusal in concert with others to provide services to one’s employer.” United Federation of Postal Clerks v. Blount, 325 F.Supp. 879, 884 (D.D.C.), aff'd mem., 404 U.S. 802, 92 S.Ct. 80, 30 L.Ed.2d 38 (1971). In Schapansky we have held that the government establishes a prima facie ease of strike participation by showing (1) the existence of a generally known strike, and (2) the employee’s unauthorized and unexplained absence from work during the strike. We further held that once the government had made that showing, “the burden of going forward with evidence to rebut that showing necessarily shifts to the employee____” Schapansky, at 482.
Since we have held that the collective bargaining agreement did not bar the Administration from cancelling Letenyei’s leave, Letenyei has not rebutted the Administration’s prima facie case that his refusal to work was unauthorized. The question, therefore, is whether Letenyei has rebutted the government’s prima facie case on the second element of striking— whether Letenyei’s refusal to work was “in concert with others.”
The presiding official held that although Letenyei “did refuse to provide services to his employer,”
there is no evidence that appellant’s refusal to do so was in concert with others or that it was connected to or a result of the PATCO strike. Rather, at all times since his leave was cancelled, appellant, had insisted that the leave cancellation was improper, in violation of the union contract, and unacceptable to him because of his moving and vacation plans.
Kays, slip op. at 5 (Phil.Reg’l Off.) (emphasis in original).
The presiding official noted that Letenyei “stated repeatedly that he never picketed, participated in the strike vote, or supported the strike.” Id. at 6. She “accepted [Le-tenyei’s] testimony as truthful.” Id. at 7.
The stated grounds upon which the Board reversed the presiding official’s decision and held that Letenyei “has failed to rebut the agency’s prima facie case in support of the charge of his participation in the PATCO strike,” Kays, slip op. at 6 (M.S.P.B.), were as follows:
The record further reveals that appellant’s absence was not due to any inability to report for work. He testified that had he received, after the commencement of the strike, direction from his supervisors to report for duty, he would have returned to work. In addition, he does not dispute that his services were intentionally withheld despite the agency’s order of August 1, 1981, requiring him to report on August 3, 1981. Moreover, while proof of an employee’s physical presence on a picket line is not an essential element of a charge of strike participation, there is evidence that appellant did so appear at various times during the strike, and in fact, that he also attended a PATCO rally on August 5, 1981.
Id. at 5 (footnote and citations omitted).
On the basis of this reasoning and analysis, we cannot sustain the Board’s decision. The fact that Letenyei was able to work during the strike period does not establish that his failure to do so was the result of his acting in concert with other controllers. It is equally compatible with his belief that his leave had been improperly cancelled and his attitude that completing his move and the sale of his house and taking his vacation were more important than prompt*533ly returning to work. Although one may condemn this attitude, its existence does not show that Letenyei’s failure to work resulted from his participation in the strike.
The presiding official accepted as “truthful” Letenyei’s testimony that “he never picketed, participated in the strike vote, or supported the strike” —although she did not explicitly so find. Although the Board stated that “there is evidence” that Leten-yei “appear[ed]” on the picket line “at various times during the strike,” it did not find that he had picketed. Nor did it give any explanation of the rejection of his testimony, which the presiding official accepted, that he had not picketed or otherwise participated in the strike.
The “evidence” of picketing to which the Board referred may have been a note in the Administration’s file “from Mr. Lang [the deputy chief of the installation] that someone reported to him that [Letenyei] was seen on the picket line one day.” Kays, slip op. at 7 (Phil.Reg’l Off.). The presiding official found this evidence insufficient to overcome Letenyei’s testimony because “[n]o document or note from that observer appears in the file, and the agency did not present either Mr. Lang or the alleged observer as witnesses at the hearing, although Mr. Lang did appear as an agency witness in the appeal of William Kays.” Id.
If that was the evidence upon which the Board relied for its conclusion that Leten-yei had been on the picket line, the Board failed to explain why, in view of the presiding official’s ruling, it nevertheless found its analysis sufficient to overcome Leten-yei’s contrary, credited testimony.
The Board also stated that Letenyei attended a PATCO rally on August 5, 1981. In his testimony Letenyei denied that he had attended a PATCO rally between August 3 and 5. He stated that he had stopped by PATCO headquarters for approximately 10 minutes because he had heard that some people he wanted to see were there, but that since they were not there, he left. He also stated that although “there was some type of a rally in progress,” he “did nqt stay around to see what it was.” Although the presiding official did not make any findings on or even discuss this incident, she “accepted” Leten-yei’s “testimony as truthful.” Once again, in dealing with this incident, the Board was required to say something more than it did.
In sum, the Board has not adequately explained its reasons for rejecting the presiding official’s determination that Letenyei rebutted the Administration’s prima facie case that his absence from work resulted from participation in the strike. The Board did not even mention its statement in its earlier decision in Trick v. Federal Aviation Administration, No. DC0752811F1144, slip op. at 6 (M.S.P.B. Dec. 17, 1981) (footnote omitted), that controllers “who successfully demonstrate that their absence from work at the time of the alleged strike resulted from ... a good faith belief that they were on approved leave, might be found not to have participated in the alleged unlawful strike.” On the basis of what the Board has said, we cannot sustain its decision.
In so holding, however, we are not ruling that on the record before it the Board could not have made a valid determination that Letenyei participated in the strike. We hold only that it has not done so.
Because of the seriousness of striking against the government, we conclude that instead of reversing the Board’s decision outright, we should vacate it and remand to the Board for reconsideration in light of this opinion. Upon the remand, the Board may make any determination it believes is justified on the basis of the record before it, but it must adequately explain the reasons for its decision. If the Board again rejects the decision of the presiding official, it must fully state the grounds for doing so. If the Board concludes that additional evidence is required before it decides the case, it may remand to the presiding official to reopen the record.
There is another point the Board may wish to consider on remand. The National Labor Relations Act protects employees engaged in concerted activities for their mu*534tual aid and protection, but not action by employees individually, from employer interference. 29 U.S.C. §§ 157, 158 (1982). An employee who stays out of work for dual motives — because he supports the strike, but also because he is afraid to cross the picket line — is viewed as participating in the strike, and therefore has engaged in protected activity. This is so because a refusal to cross the picket line “based on fear and nothing else,” does not constitute action in concert with other employees. N.L.R.B. v. Union Carbide Corp., 440 F.2d 54, 56 (4th Cir.), cert. denied, 404 U.S. 826, 92 S.Ct. 58, 30 L.Ed.2d 55 (1971); see also Coors Container Co. v. N.L.R.B., 628 F.2d 1283, 1287-88 (10th Cir.1980); Virginia Stage Lines v. N.L.R.B., 441 F.2d 499, 502 n. 3 (4th Cir.), cert. denied, 404 U.S. 856, 92 S.Ct. 105, 30 L.Ed.2d 98 (1971).
Unlike the situation under the National Labor Relations Act, where employee action is protected only if it is concerted but not if it is individual, the opposite situation exists for federal employees, who engage in strike action (which is a crime) only if they withhold service in concert with others but not individually. Perhaps, by analogy, a government employee who stays away from work, both for non-strike related motives and also because he supports the strike, could be viewed as striking. Cf. Jones v. T.V.A., 1982 Fed.Merit Sys.Rep. H 7008 (M.S.P.B. Feb. 19, 1982), and Duckett v. T.V.A., 1982 Fed.Merit Sys.Rep. f 7013 (M.S.P.B. Feb. 19, 1982), where the Board drew upon precedents under the National Labor Relations Act, including Union Carbide, in determining questions of strike participation by government employees. As noted, there is some evidence in the record indicating that Letenyei’s actions reflected his participation in the strike. Of course, we express no views on this issue but indicate only that the Board may consider the question on the remand if it so wishes.
Finally, if the Board were to hold that Letenyei had not participated in the strike, it should consider the correctness of the 60-day suspension the presiding official substituted for the removal the Administration ordered — if it concludes that that issue was properly raised before it.
C. Letenyei makes a number of other contentions, all of which are dealt with in the other air traffic controller cases we decide today. Accordingly, we need not address them.
CONCLUSION
The decision of the Merit Systems Protection Board sustaining the Administration’s removal of petitioner Letenyei is vacated, and the case is remanded to the Board for further proceedings consistent with this opinion.
VACATED AND REMANDED.