All the discussion of GPS is interesting, but not really relevant for the SR-71 for most of its career. SR-71 first flight was December 1964, IIRC. 20+ years before GPS. Automated astral navigation, on the other hand, was developed for cruise missiles (like the Snark) starting in the mid fifties, and would have been a "mature" technology by 1964.
Last edited by Weight and Balance; 16th October 2003 at 10:30.