966 was lost on the night of Thursday, April 13, 1967.   She crashed near Las Vegas, New Mexico (not Nevada) after entering an unrecoverable stall following an in-flight refueling.   Both pilot Cpt. Earle Boone and RSO Cpt. Richard "Butch" Sheffield ejected safely.  

Flight records for this aircraft are a little unclear; the June 1967 DCMA Summary of Individual Aircraft shows total time on the airframe to be 53.2 hours; however, the March 1967 SR-71 Flying Activity Summary shows the total time to be 63.3 hours at the conclusion of her March 31 flight.  Considering that the only flight she made in April 1967 was her final one of 1hr23min, that would make the total time 64.7 hours.  Sheffield estimates that 966 had less than 50 hours of flight time on her at the time of the crash, lending creedence to the 53.2 hour figure.  Statistics were kept on both flight hours scheduled and flight hours flown; allowing for aborted and cancelled flights, the 53.2 hour mark is more likely.