Additionally advances in Soviet anti-aircraft missile design had resulted in the "fly high and fast" invulnerability idea becoming outdated as had already been proved by the shooting down of Francis Gary Powers Lockheed U2 Spy-plane in May 1960 whilst over Soviet territory.
It is of note that following a photo-shoot on the 8th of June 1966 the second prototype Valkyrie tragically crashed after a collision with a F-104 Starfighter, it is thought that the F-104 Starfighter was rolled into the Valkyrie prototype by the wake vortex produced by the Valkyrie's wingtip.
North American XB-70A Valkyrie Specifications:
- Crew: Pilot and Co-Pilot
- Length: 185 ft 10 in (56.6 m)
- Wingspan: 105 ft 0 in (32 m)
- Height: 30 ft 9 in (9.4 m)
- Empty weight: 210,000 lb (93,000 kg)
- Loaded weight: 534,700 lb (242,500 kg)
- Max takeoff weight: 550,000 lb (250,000 kg)
- Engines: Six 28,800 lbf(128 kN) General Electric YJ93-GE-3 afterburning turbojets
- Maximum speed: Mach 3.1 (2,056 mph, 3,309 km/h)
- Cruise speed: Mach 3.0 (2,000 mph, 3,200 km/h)
- Range: 4,288 mi ( 6,900 km)
- Service ceiling: 77,350 ft (23,600 m)