In the mid-1950s the USAF issued a General Operating Requirement for a supersonic trainer, planning to retire its 1940s-era Lockheed T-33s.
Most T-38s built were of the T-38A variant, but the USAF also had a small number of aircraft converted for weapons training (designated AT-38B), which were fitted with a gunsight and could carry a gunpod, rockets, or bombs on a centerline pylon.