The Lockheed D-21 is an American supersonic reconnaissance drone. The D-21 was initially designed to be launched from the back of an M-21 carrier aircraft, a variant of the Lockheed A-12 aircraft. The drone had maximum speed in excess of Mach 3.3 at an operational altitude of 90,000 feet. Development began in October 1962. Originally known by the Lockheed designation Q-12, the drone was intended for reconnaissance deep into enemy airspace.