The Kreider-Reisner XC-31 or Fairchild XC-31 was an American single-engined monoplanetransport aircraft of the 1930s designed and built by Kreider-Reisner. It was the largest single-engine aircraft built to that time, as well as one of the last fabric-covered aircraft tested by the U.S. Army Air Corps. Designed as an alternative to the emerging twin-engined transports of the time such as the Douglas DC-2, it was evaluated by the Air Corps at Wright Field, Ohio, under the test designation XC-941, but rejected in favor of all-metal twin-engined designs.
The XC-31 was built with an aluminum alloy framework covered by fabric, and featured strut-braced wing and a fully retractable landing gear, the main gear units mounted on small wing-like stubs and retracting inwards. An additional novel feature was the provision of main cargo doors that were parallel with the ground to facilitate loading.