Designed to carry 25 tons of nuclear bombs at three times the speed of sound and at an altitude of 19 miles, everything about the awesome XB-70 Valkyrie was superlative. On its first appearance in 1964, the six-engined XB-70 was at once the heaviest, most powerful, and most costly aircraft ever built. It narrowly missed also being the fastest and longest-ranged. Its development resulted in over 700 patents being lodged, and its combination of size and performance remains unmatched today. One test pilot described flying the Valkyrie at three times the speed of sound as like “driving a Greyhound bus around the racetrack at Indianapolis.” And yet only two prototypes were ever built. As a bomber, the B-70 was stillborn.
Advances in surface-to-air missile technology negated its height and speed as protection and led to its cancellation—hastened by the loss, after a midair collision, of one of the prototypes. The challenge of building the B-70 remains arguably the most demanding ever to face a US aircraft manufacturer. The aviation writer Bill Gunston put it well (as he always does):
“In future, when a harassed aircraft engineer feels something is too difficult, he can derive solid comfort from the B-70. Compared with that, his problem—whatever it is—is a pushover.”
