Despite its technical triumphs and support from aviators, the XB-70’s operational future unraveled almost as quickly as it ...

The first prototype, XB-70A-1, rolled out on May 11, 1864, in Palmdale, California, and made its maiden flight on September 21 of that year. A second prototype, XB-70A-2 followed in 1965.

The XB-70 Valkyrie could cruise at Mach 3, riding its own shock wave to do so, and could hit altitudes of 70,000 feet. But the XB-70 Valkyrie never went into full-scale production ...