 For example, the CAR 3 authority for modification and replacement parts could be found in section 3.18 after 1952.In 1955, the Civil Aeronautics Board separated the parts authority out of the airworthiness standards, and placed it in a more general location so that one standard would apply to replacement and modification parts for all different forms of aircraft.In 1965 CAR 1.55 became Federal Aviation Regulation section 21.303.