The 503d Air Defense Group is an inactive United States Air Force organization. Its last assignment was with the 25th Air Division of Air Defense Command at Portland International Airport, Oregon. It was inactivated on 18 August 1955. The group was originally activated as a support group at the end of World War II and provided logistics and administrative support for the 86th Fighter Group in Germany until 1946, when the group returned to the United States, where it supported the 56th Fighter Group. It was discontinued when the USAF reorganized its combat and support units on its bases into a single wing. The group was activated once again in 1953, when ADC established it as the headquarters for two dispersed fighter-interceptor squadrons and the medical, maintenance, and administrative sq