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-kilograms (2,000-lbf).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 November 30, 1943, the MX-324 made its maiden powered flight on July 5, 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 October 2, 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.