The XB-70 Valkyrie began as North American Aviation's answer to a Cold War problem: how to build a bomber that could outrun Soviet interceptors rather than dodge them. Designed for Strategic Air Command in the late 1950s as a nuclear-armed deep-penetration aircraft, it was built around six engines, a delta-wing airframe, and folding wingtips meant to ride its own shockwave at Mach 3-plus while cruising at 70,000 feet. This episode of the Wings series traces that design through the engineering problems it created, from the exotic fuels and materials needed to survive sustained supersonic flight to the shifting Air Force strategy that made a manned bomber look obsolete just as it neared completion in 1964. Archival footage and test-program detail carry the story of a program that never went into full production but left its mark on later supersonic aircraft. It stands as one of the most ambitious airframes ever built for a mission the Pentagon ultimately decided it no longer needed.