This was one of the two prototype YAT-37Ds evaluated by the USAF for a counter-insurgency (COIN) attack/reconnaissance aircraft to use in Southeast Asia. It was retired to the museum in December 1964. However, it was recalled to active service in August 1966 for final design testing of the urgently needed A-37 attack aircraft. It rejoined the museum in July 1970 as a YA-37A

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.