Designed by John Thorpe and Rudy Paulic in 1933 and built at the Boeing School of Aeronautics to test and teach advanced concepts, the T-3 first flew in 1939. Development stopped during World War 2 as Boeing concentrated on military projects. Rudy Paulic replaced the 125 hp Warner radial engine with a 180 hp Lycoming with a controllable pitch propeller and made the landing gear retractable in 1959.