The SNCAC NC.3021 Belphégor was a French high altitude research aircraft designed and built at the end of World War II.

When work on the design resumed at the war's end these engines were replaced with a similarly arranged Daimler-Benz pair, resulting in a revised type, the NC.3021.

The crew positions were also in the pressurized region: the pilot's cockpit placed his head above the upper fuselage under a clear canopy.

[1][3] Its semi-monocoque fuselage was in three sections; the metal forward part contained the German-designed 2,200 kW (2,950 hp) Daimler-Benz DB 610A twin-crankcased "power system" engine unit weighing some 1.5 tonnes by itself, with its circular radiator in the nose and driving a single four blade propeller as well as the pressurization system.

Flight tests were made difficult, if not dangerous, by the DB 610's tendency to overheat and they were abandoned either in 1947 in the absence of financial support[4] or in 1949, after only forty flying hours, because of the continuing mechanical problems.