Half a century before the B-2 stealth bomber entered service, the aircraft manufacturer John K. Northrop was already developing piston-engined prototypes that looked remarkably similar. A "flying wing" is theoretically very efficient, offering superior range and payload. With the USAAF hungry for such aircraft during World War II, Northrop, a flying wing enthusiast, was contracted to design a 172ft-span bomber. Fifteen XB-35/YB-35 airframes were built,...