Fascinating Look Back at the XB-70 Valkyrie, the World’s Fastest Nuclear Strategic Bomber That was Capable of Cruising at Mach 3+

The North American Aviation XB-70 Valkyrie, first flown on September 21, 1964, is still considered to be the world’s fastest nuclear strategic bomber ever. It was essentially the prototype version of the planned B-70 nuclear supersonic strategic bomber for the United States Air Force Strategic Air Command. This aircraft was designed in the late 1950s by North American Aviation (NAA), and what set it apart from the others is its ability to cruise for thousands of miles at Mach 3+ while flying at 70,000 feet.

When flying at Mach 3+, it was expected that the B-70 would be nearly invisible to interceptor aircraft. The aircraft would spend only a brief time over a particular radar station, flying out of its range before the controllers could position their fighters in a suitable location for an interception. These speeds also made it tough to see on radar displays at the time, while its high-altitude and high-speed capacity had not yet been matched by any contemporaneous Soviet interceptor or fighter aircraft.

Unfortunately, the Soviet’s first surface-to-air missiles in the late 1950s put the near-invulnerability of the B-70 in doubt, so the US Air Force began flying its missions at low level, where the missile radar’s line of sight was limited by terrain. However, this meant that the B-70 offered little additional performance over the B-52 it was meant to succeed, while being far more expensive with shorter range. So, the entire program was shut down in 1961, although two prototype aircraft exist, both designated XB-70A. Only one of these prototypes survived testing, and can be seen at the National Museum of the United States Air Force near Dayton, Ohio.