Before 1974, railroad retirees received benefits from the Social Security and railroad retirement systems. In 1974, Congress passed an act changing the benefit plans, favoring some retirees over others. Some workers qualified for dual benefits, some did not. Fritz (P) and other employees who did not qualify for dual benefits under the new law challenged it as a violation of equal protection. Appellee and others filed this class action seeking a declaratory judgment that it is unconstitutional under the Due Process Clause of the Fifth Amendment because it irrationally distinguishes between classes of annuitants. Appellee contended below that it was irrational for Congress to have drawn a distinction between employees who had more than 10 years but less than 25 years of railroad employment simply on the basis of whether they had a 'current connection' with the railroad industry as of the changeover date or as of the date of retirement. The District Court agreed with appellee that a differentiation based solely on whether an employee was 'active' in the railroad business as of 1974 was not 'rationally related' to the congressional purposes of ensuring the solvency of the railroad retirement system and protecting vested benefits.