The Horten boys kept tinkering, and by 1932 had developed an all-wing glider, made largely of wood and linen, that actually got off the ground—though it had some stability problems. In 1943 ...

“There’s not a straight line on it anywhere,” boasts the Northrop Grumman engineer, sighting the prototype’s gently swelling 15-meter (49 feet) elliptical wings. From above, the wings look ...