In Air Line Pilots v. O'Neill, 499 U. S. 65, 67 (1991), the Supreme Court specifically considered the appropriate standard for evaluating conduct under the "arbitrary" prong of the duty of fair representation. The Supreme Court held that under the "arbitrary" prong, a union's actions breach the duty of fair representation "only if the union's conduct can be fairly characterized as so far outside a `wide range of reasonableness' that it is wholly `irrational' or `arbitrary.' " 499 U. S., at 78. In Air Line Pilots, the union had negotiated a settlement agreement with the employer, which in retrospect proved to be a bad deal for the employees. The fact that the union had not negotiated the best agreement for its workers, however, was insufficient to support a holding that the union's conduct was arbitrary. 499 U. S., at 78-81. A union's conduct can be classified as arbitrary only when it is irrational, when it is without a rational basis or explanation. Ibid. In Air Line Pilots Ass'n, Int'l v. O'Neill, 499 U.S. 65, 67, 111 S.Ct. 1127, 1130, 113 L.Ed.2d 51 (1991) ("ALPA "), the Court explained that a "settlement is not irrational simply because it turns out in retrospect to have been a bad settlement." Id. 499 U.S. at 79, 111 S.Ct. at 1136. In that case, a group of airline pilots engaged in a choleric strike when Continental Airlines repudiated its collective-bargaining agreement with the pilots' union and reduced the pilots' salaries and benefits. The pilots alleged that the union violated its duty of fair representation by settling the dispute with Continental Airlines on potentially worse terms than if the pilots themselves had unilaterally abandoned the strike. Whereas the striking pilots desired reinstatement strictly according to seniority, the settlement agreement permitted Continental to allocate numerous Captain positions to nonstriking pilots, irrespective of the nonstriking pilots' seniority. The Court rejected the pilots' claim against the union because, at the time settlement was made, Continental appeared resolute about ignoring the striking pilots' seniority and giving first priority to all nonstriking pilots. Id. 499 U.S. at 78-82, 111 S.Ct. at 1136-37. At the very least, the settlement produced certain and prompt access to a share of the new jobs and avoided the costs and risks associated with major litigation.... In labor disputes, as in other kinds of litigation, even a bad settlement may be more advantageous in the long run than a good lawsuit. Id. 499 U.S. at 81, 111 S.Ct. at 1137.