Completion of the first A-12 was delayed several times because the performance specifications it had to meet put Johnson and the Skunk Works in uncharted territory. The aircraft, over 101 feet long and weighing up to 62 tons fully loaded, had to fly at Mach 3.2, or 2,150 miles per hour—as fast as a rifle bullet—at a mid-range altitude of 91,000 feet. The A-12 was expected to be over four times faster than the U-2 and go almost three miles higher.