On December 22, 1964, the first flight of the D-21/M-21 combination (now referred to as the “M/D-21”) was successfully completed from Groom Lake. Per Johnson: "Bill Park flew at the end of the day. It flew well and, in spite of having low-powered engines, went supersonic on the first flight." Interestingly, on this same day, the first SR-71A successfully completed its first flight from Lockheed's Palmdale, California facility.