Lockheed M-21 Blackbird & D-21B Drone

The Lockheed D-21B, shown in the above photo mounted atop the M-21,  was an advanced reconnaissance drone developed in the 1960s during the Cold War. It was designed to fly at speeds exceeding Mach 3.3 (over 2,200 mph) and altitudes above 90,000 feet, making it virtually invulnerable to interception. Originally intended to be launched from the back of the specialized M-21 carrier aircraft (a variant of the SR-71 Blackbird), the program was redesigned following a fatal accident during testing, resulting in the D-21B variant that was launched from beneath the wing of a B-52 bomber.

What makes the D-21B unique is its completely autonomous nature. Once launched, it would follow a pre-programmed route over the target area, take photographs, and then jettison the film canister for mid-air recovery before the D-21B self-destructed. Despite these advanced capabilities, the program was canceled after four unsuccessful reconnaissance flights over China. Most D-21 drones were scrapped, though a few survive today in museums.