One summer afternoon in 1917, Royal Flying Corps trainee Graham Donald prepared to try a new maneuver with his Sopwith Camel. He ascended into a vertical loop, intending to flip the plane at the top and fly off in the opposite direction. Unfortunately, when the airplane was fully inverted at 6,000 feet, his safety belt gave way and “suddenly I dived clean through it and fell out of the cockpit.” “The first 2,000 feet passed very quickly, and terra firma looked damnably ‘firma,'” he recalled later. But as he fell, “I began to hear my faithful little Camel somewhere nearby.”...