The MX-324 was a rocket-powered prototype used in the design study of the Northrop XP-79, a proposed rocket-powered military interceptor. The MX-324 had a length of 4.3 meters and a wingspan of 11.6 meters. It was powered by Aerojet XCAL-200 rocket motor that used monoethylaniline and red fuming nitric acid and developed a thrust of 91-kilogram (2,000-pound-force).The pilot lay in a prone position, enabling the design to be a true all-wing aircraft with no protruding cockpit. After an initial glide test on 30 November 1943, the MX-324 made its maiden powered flight on 5 July 1944, at Harper Dry Lake, California, with test pilot Harry Crosby at the controls. It was towed to an altitude of 8,000 feet by a P-38 before being released. It then fired its engine and flew for more than four minutes before gliding to a safe landing.

In addition to the single MX-324, two unpowered MX-334 gliders were built and tested, the first making its maiden flight on 2 October 1942 at Muroc. In the case of both the MX-324 and MX-334, plywood was used for most of the airframe with the exception of the load-carrying center section, which was manufactured from welded metal tubing.