"ON OCTOBER 30, 1958, representatives of six of the nation's twelve domestic trunk-line carriers and one international carrier signed an agreement, effective retroactively to October 20,1958, establishing a program for the partial protection of struck participants against the normal economic losses associated with a strike period. The plan is known as the "Mutual Aid Pact." The original six carrier signatories and the four other trunk-line carriers who later joined the pact usually account for approximately 90 percent of the annual trunk-line traffic carried in the nation."