11/30/2011. Preliminary design work on the single-seat interceptor JA 37 began in 1968. Flight testing of selected systems, including the radar, was initiated in early 1973 in a modified Saab 32 Lansen development aircraft. Four modified AJ 37s were used in the JA 37 development program, the first of these, for control system tests, flew for the first time in June 1974.

The second development aircraft (pictured here) was used for engine tests and made its first flight with an RM8B engine on September 27, 1974. This aircraft was also fitted with an 1.18 in (30 mm) Oerlikon long-range cannon, installed in an underbelly pack, aft of which was a redesigned ventral fin. It was lost eleven months later, August 27, 1975.

The third (first flight November 22, 1974) and fourth development aircraft were used for electronics and armament system tests respectively. The fifth development aircraft that flew in 1975, was built from the outset to JA 37 standard, and was followed by 149 production JA 37s.