Lockheed D-21

The Lockheed D-21 was an American Mach 3+ reconnaissance drone. The D-21 was initially designed to be launched from the back of its M-21 carrier aircraft, a variant of the Lockheed A-12 aircraft. Development began in October 1962. Originally known by the Lockheed designation Q-12, the drone was intended for reconnaissance missions deep in enemy airspace.

The D-21 was designed to carry a single high-resolution photographic camera over a preprogrammed path, then release the camera module into the air for retrieval, after which the drone would self-destruct. Following a fatal accident when launched from an M-21, the D-21 was modified to be launched from a Boeing B-52 Stratofortress. Only four operational D-21 flights were made over the People's Republic of China before the program was canceled in 1971.