The North American Aviation XB-70 Valkyrie was the prototype of the B-70 nuclear-armed, deep-penetration strategic bomber for the U.S. Air Force's Strategic Air Command. North American Aviation designed the Valkyrie bomber as a large, six-engine aircraft capable of reaching Mach 3+ while flying at 70,000 feet (21,000 m); these speed and altitude capabilities would allow the evasion of interceptor aircraft, the only effective weapon against bomber aircraft at the time.

Due to improved high-altitude surface-to-air missiles (SAMs), the U.S. Air Force's doctrine changed to low-level penetration bombing, the large development costs of the B-70 program, and the introduction of intercontinental ballistic missiles (ICBMs) to the U.S. nuclear arsenal, led to the cancellation of the B-70 program in 1961. As such, two prototype aircraft were built, and designated XB-70A; these aircraft were used for supersonic test-flights during 1964-69. In 1966, one prototype crashed after colliding in midair with a smaller jet aircraft; the remaining Valkyrie bomber is in the National Museum of the United States Air Force, in Ohio.