|521st Air Defense Group
|Branch||United States Air Force|
|Part of||Air Defense Command|
The 521st Air Defense Group is a disbanded United States Air Force organization. Its last assignment was with the 31st Air Division at Sioux City Municipal Airport, Iowa, where it was inactivated in 1955. The group was originally activated as a support unit for the 310th Bombardment Group at the end of World War II in Italy and then redeployed to the United States where it was inactivated in 1945.
The group was activated once again in 1953, when ADC established it as the headquarters for a dispersed fighter-interceptor squadron and the medical, maintenance, and administrative squadrons supporting it. It was replaced in 1955 when ADC transferred its mission, equipment, and personnel to the 53d Fighter Group in a project that replaced air defense groups commanding fighter squadrons with fighter groups with distinguished records during World War II.
The group was first activated as the 521st Air Service Group in a reorganization of Army Air Forces (AAF) support groups in which the AAF replaced Service Groups that included personnel from other branches of the Army and supported two combat groups with Air Service Groups including only Air Corps units. It was designed to support a single combat group. Its 947th Air Engineering Squadron provided maintenance that was beyond the capability of the combat group, its 771st Air Materiel Squadron handled all supply matters, and its Headquarters & Base Services Squadron provided other support. The group supported 310th Bombardment Group in Italy. The group returned to the US in 1945 and was inactivated. It was disbanded in 1948.
The group was reconstituted, redesignated as the 521st Air Defense Group, and activated at Sioux City Municipal Airport in 1953 with responsibility for air defense of central Midwestern United States. It was assigned the 87th Fighter-Interceptor Squadron (FIS), which was already stationed at Sioux City Airport, and flying World War II era North American F-51 Mustangs as its operational component. The 87th FIS had been assigned directly to the 31st Air Division. The group replaced 79th Air Base Squadron as the host USAF unit at Sioux City Municipal Airport. It was assigned three squadrons to perform its support responsibilities.
In the fall of 1953 the 87th FIS upgraded to radar equipped and Mighty Mouse rocket armed North American F-86 Sabre jet aircraft and the 14th FIS, also flying "Sabres", was activated as the group's second operational squadron. In November 1954 the 87th FIS moved to England and was reassigned. The 87th FIS was replaced the next month by the 519th FIS, another "Sabre" squadron. The group was inactivated and replaced by the 53d Fighter Group (Air Defense) in 1955 as part of Air Defense Command's Project Arrow, which was designed to bring back on the active list the fighter units which had compiled memorable records in the two world wars. Disbanded once again in 1984.