The North American AviationXB-70 Valkyrie was an experimental, large bomber jet made for a USAF requirement of a nuclear-armed, deep-penetration strategic bomber for the Strategic Air Command of the U.S. Air Force during the 60s. Only two were built.
The Valkyrie was a very advanced for its time six-engine bomber aircraft jet with canards capable of reaching Mach 3+ while flying at 70,000 feet (21,000 m). Its maiden flight was on 1964.
The program was canceled due to cost overruns, changing needs of the air-force, improvements in high-altitude surface-to-air missiles (SAMs), the introduction of intercontinental ballistic missiles (ICBMs) to the U.S. nuclear arsenal and the unfortunate mid air collision of one of the prototypes with an F-104 Starfighter.
The remaining one served as a research plane for NASA before being retired to the National Museum of the United States Air Force in 1969.
