Interstate Aircraft and Engineering Corporation was a small American aircraft manufacturer from April 1937 to 1945, based in El Segundo, California. In 1940 they developed the Cadet, a 2-seat monoplane. The Model S-1B was developed into the XO-63, later redesignated to the XL-6. Two hundred fifty-nine of the XO-63/L-6/L-8 series were built for the USAAF. Assets of the company were sold to the Harlow Aircraft Company in 1945.