Piggyback Airplanes

Ten of aviation’s most famous hitch-hikers


Disposable Spy

(Department of Defense)

Hitchhiker: Lockheed D-21 drone
Mothership: Lockheed M-21
United States, 1966

As the cold war escalated in the early 1960s, so did the spying game. Speed, stealth, and zero casualties were the primary objectives when Lockheed’s Skunk Works began work on the D-21 unmanned aerial vehicle (UAV) under the name Tagboard.

This highly classified, 43-foot-long, syringe-like drone had anti-radar coating and could fly reconnaissance missions up to 80,000 feet, at Mach 3-plus and out to 3,000 miles.

The D-21 was mounted on the top, tail-end of its M-21 mothership (fittingly, their designations were for “daughter” and “mother”), a variation on the A-12 spyplane. Launching the drone was a tricky maneuver that required igniting the D-21’s ramjet engine and threading it between the M-21’s twin tails.

After surveying enemy territory, the D-21 returned to a pre-determined, over-water location, slowed to Mach 1.6, and ejected its high-resolution camera to be retrieved in-air or plucked from the water. With its mission complete, the D-21 would be destroyed by remote command.

Tagboard’s life was brief, however: Full testing started and stopped in 1966. The first three launches succeeded. In the fourth flight, the drone collided with the M-21, shearing off parts of the right wing, rudder, and engine. The two crew members ejected into the ocean, and one drowned.

Lockheed immediately scrapped the project, but pursued a variation by modifying the drone into the D-21B, which used a solid rocket booster and was drop-launched from the larger Boeing B-52H. The new pairing barely outlived the first. Each of its four flights to spy on China’s Lop Nor nuclear test site failed: The drone crashed once in Russia and once in China, and the two times it completed the flight, the camera payloads were lost at sea. The program was axed.


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