The engines of the XB-70 Valkyrie. The aircraft was a prototype bomber designed to cruise at Mach 3. Two were built and flown. Serial number 2 was destroyed in 1966 after a mid-air collision with an F-104 during a formation flight for a photoshoot. Serial number 1 flew from 1964 through 1969, when it was flown to its current home at the museum.