North American XB-70 Valkyrie

The Aviation XB-70 Valkyrie was the prototype version of the planned B-70 nuclear-armed, deep-penetration supersonic strategic bomber for the Air Force Strategic Air Command.

Designed in the late 1950s by Aviation (NAA), the six-engined Valkyrie was capable of cruising for thousands of miles at Mach 3+ while flying at 70,000 feet (21,000 m).

Videos

Deep dive explanation.
Historical context.
General overview.