Under the Railway Labor Act (RLA), a dispute about forming or modifying a collective bargaining agreement that has not been resolved through required National Mediation Board mediation or voluntary interest arbitration. Rail and air carriers, or the unions representing their employees, may seek intervention from federal courts to resolve a major dispute. The parties may also inflict economic harm on the other through self-help (such as strikes or lockouts), after RLA-mandated cooling-off periods, to force the other party to reach an agreement to resolve the dispute.

Major disputes are distinguishable from three other types of disputes flowing from the RLA:

For more information, see Practice Note, Railway Labor Act: Overview.