* Astronomy

The North American Aviation XB-70 Valkyrie was the prototype version of the proposed B-70 nuclear-armed deep-penetration strategic bomber for the United States Air Force's (USAF) Strategic Air Command. Designed by North American Aviation in the late 1950s, the Valkyrie was a large six-engined aircraft able to fly Mach 3+ at an altitude of 21,000 m, which would have allowed it to avoid interceptors, the only effective anti-bomber weapon at the time. 
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The first flight of the XB-70 Valkyrie was on the 21st September 1964