In 1943 the Chase Aircraft Company was founded to undertake the design, development and production of a heavy assault glider for the USAAF. The company built two XCG-14 gliders, followed by two XCG-18As. These were similar, but of all-metal construction. Of high-wing configuration, with a tail held high off the ground above a rear loading ramp and with a square-section fuselage, the XCG-18A offered potential as a powered transport. Consequently, the second airframe (47-641) was fitted with a pair of R-2000-11s and assigned the designation YC-122. Two more were built in 1949 as YC-122As (48-1369, 48-1370), of which the second was re-engined with R-1820-101s to become the YC-122B. This engine was used for the service trials batch of nine YC-122Cs, which survived in limited USAF service from some years in the 1950s.