The Vultee Valiant started out as a private venture, the Vultee Model 54, and was tested by the United States Army Air Corps (USAAC). in 1938. The Vultee Model 54 had a Wright R-1340 (600 HP) engine and retractable landing gear. This was considered to powerful and complicated for basic training. Vultee redesigned the plane to have fixed landing gear and a less powerful engine.
Pratt & Whitney couldn't keep up with production of their R-985 Wasp engines so Wright produced around 1,700 R-975 Cyclones that were fitted in the BT-15.