What You Need to Know: The North American XB-70 Valkyrie epitomized Cold War aerospace innovation. Designed to replace the B-52, the Valkyrie boasted speeds exceeding Mach 3 and an altitude ...

The new bomber never replaced the B-52. But the XB-70 was an impressive machine. Capable of achieving Mach three-plus speeds and a 70,000-foot ceiling, the XB-70 featured six engines.