Article 123 was the third A-12 built and the first to crash. It was powered by Pratt & Whitney J75 engines and so never attained its design speed of Mach 3. It was lost on 24 May 1963.
On May 24, 1963, CIA pilot Ken Collins (mission callsign DUTCH 26) took Article 123 up for its 79th flight. He was scheduled to perform subsonic engine tests because fuel control problems plagued the A-12 during acceleration and cruise. Collins also planned to gain proficiency with the inertial navigation system (INS). He took off to the north from Area 51 with Capt. Donald J. Donohue (call sign BOXER 11) flying safety chase in a McDonnell F-101B. They climbed to a cruising altitude of 25,000 feet and then executed a right turn over the town of Austin, climbing to 27,000 feet to avoid cloud formations. Donohue stayed close to observe the A-12's engine nacelles and exhaust ejector sections. Collins and Donohue soon entered the Wendover restricted area on the edge of Utah's Great Salt Lake Desert. They turned over the town of Wendover and flew southwest toward Area 51. As the two airplanes completed one circuit of the training route, Jack Weeks (call sign BOXER 10) relieved Donohue and the formation headed north again, the pilots vigilant for increasing clouds.
Nearing the Utah border, they cruised at Mach 0.85 at an altitude of 34,000 feet as heavy cumulus and cirrus cloud formations built up below. About 33 nautical miles from Wendover, Weeks asked Collins for his fuel quantity. "Ninety-five hundred pounds," he replied. It was about ten minutes before noon. The A-12 and F-101 were flying a tight formation. At the Wendover checkpoint, Collins began a planned left turn and climb. About a third of the way through the turn, Weeks heard a warning horn in the cockpit that signaled his airspeed was getting too slow. Wanting to avoid a pitch-up, Weeks extended his turn and built up airspeed, but he intermittently lost sight of the A-12 due to the cirrus overcast. As the two planes rolled out of the turn, the F-101 was slightly ahead and above the A-12. Weeks advised Collins that he was crossing in front of him and climbing higher to get out of the clouds.
Collins, meanwhile, noticed an anomaly on his instrument panel. Although his throttle setting was constant and the airplane was climbing, the indicated airspeed and Mach number appeared to be increasing. Collins retarded the throttles slightly, leveled off on top of the clouds and set the INS to Auto-Navigation mode. Now the airspeed indication began to decrease. Assuming this was a temporary malfunction, Collins began checking his mission equipment and engine instruments. All were functioning properly. He also checked the pitot heat switch, which had been on during the entire flight. Collins flipped it off and on three times, finally leaving it on. "I think I'm having airspeed trouble," he told Weeks.
Suddenly, Collins noticed that his airspeed was decreasing below the cruise setting. He lowered the A-12's nose slightly to increase airspeed while avoiding the thick cumulus clouds below. As the indicated airspeed continued to decrease, he increased his rate of descent. Since the airspeed failed to increase, Collins decided either the pitot system or the airspeed indicator was malfunctioning. He leveled off and engaged the autopilot, but the readings continued to decrease.