In the early 1960s, the USAF determined that a new light attack aircraft was needed for the counter-insurgency (COIN) operations prevalent in the myriad Third World nations that could not afford to purchase and operate, and in reality did not have a military requirement for, the current generation of high-performance fighter aircraft.

In 1962, the original T-37C prototype aircraft (62-5951) and a subsequently modified T-37B (62-5950) were evaluated by the USAF as armed COIN aircraft at Eglin AFB, Florida, at the Special Air Warfare Center. These prototype aircraft still carried the same 1,025-pound-thrust Continental J69-T-25 engines used in the basic T-37B, although the aircraft gross weight was increased to 8,700 pounds. The USAF objective was to develop a lightweight, easily maintained attack fighter with excellent short field performance. It was soon clear that these first prototypes needed more power to achieve the latter objective.

In 1963, the USAF Aeronautical Systems Division at Wright-Patterson AFB near Dayton, Ohio, issued a contract to Cessna for two YAT-37D prototypes for evaluation. To meet the six-month delivery schedule, Cessna used the prototypes previously evaluated at Eglin AFB as the airframes for the new prototypes. The biggest challenges were the 10,500-pound gross weight and the speed and short-field performance requirements. To meet these…