Ca.1962: TOS USAF as a T-37B, then modified as the prototype T-37C. 1963: Converted to YAT-37D as prototype for a counter-insurgency attack aircraft; was given engines of 2400 lbst and six underwing pylons as well as the wing-tip fuel tanks. 12/64: Flown to the Air Force Museum. 8/66: Returned to service with the USAF due to high losses of A-1 Skyraiders in Vietnam. Testing was resumed as the aircraft was redesignated YA-37A as a prototype for the A-37A, and later brought up to A-37A standards. 7/70: Flown to the Air Force Museum.

In the early 1960s, the USAF investigated the conversion of the Cessna T-37 jet-powered primary trainer for counterinsurgency missions. This lead eventually to the successful development of the YA-37A and the subsequent conversion of 39 T-37s into A-37s for use in Vietnam. This YA-37A was retired to the National Museum of the USAF for display in July 1970.