The XB-70 Valkyrie

The XB-70 Valkyrie was a nuclear-armed bomber designed for the USAF's SAC in the 1950s. A 6-engined aircraft able to fly at Mach 3 at high altitudes (74,000 ft), which would have allowed it to avoid defending interceptors, the only effective anti-bomber weapon at that time. The cost of the aircraft ($1.5Bn USD), the development of ICBMs and the first effective anti-aircraft missiles led to the cancellation of the program in 1961. Music: David Axelrod - "Holy Thursday".