North American Aviation's B-70 Valkyrie was a nuclear-armed bomber designed for the United States Air Force's Strategic Air Command in the 1950s. The Valkyrie was a large six-engined aircraft able to fly at Mach 3 at high altitudes, which would have allowed it to avoid defending interceptors, the only effective anti-bomber weapon at the time. The proposed cost of the aircraft, along with changes in the technological environment due to the introduction of the first effective anti-aircraft missi… (More on Xb-70)