Intruder from the Future or B-70 Valkyrie The B-70 Valkyrie was supposed to be the aviation dream from the future, but while it was developed, the improvements of high-altitude surface-to-air missiles, the change to low-level penetration bombing, the program's high development costs, and the introduction of intercontinental ballistic missile (ICBMs) led to the cancellation of the B-70 program in 1961.