The United States Court of Appeals for the Third Circuit has held that the 1978 amendments to the Age Discrimination in Employment Act are to be applied prospectively because retrospective application would result in manifest injustice.
Sikora v. American Can Co., 622 F.2d 1116 (3d Cir. 1980).
Andrew C. Siminerio,
Labor Law - Involuntary Retirement - Age Discrimination in Employment Act - Retroactive Application of Statutes,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol19/iss2/8