On March 20, 1971, a specially modified US Air Force B-52 bomber from the 4200th Support Squadron took off from Andersen Air Force Base in Guam carrying a unique aircraft mounted under its wing. The aircraft, shaped like a dart and painted black, was a D-21 supersonic reconnaissance drone. It was to be the fourth such drone to conduct aerial reconnaissance of China's Lop Nor nuclear test site in northwestern China, and despite its sophistication, it would crash into the very country it was intended to spy on. Created by the renowned Lockheed Corporation, the D-21 was the most advanced...