The CIA sought to replace the vulnerable U-2 spy plane with a successor that could fly faster and higher than Soviet defenses. After considering proposals from Lockheed and Convair, the CIA selected Lockheed's A-12 design in 1959, which would use powerful new engines to cruise at Mach 3 at over 90,000 feet. Lockheed's Skunk Works division, led by aviation pioneer Kelly Johnson, refined the A-12's design through wind tunnel tests and mockups to ensure it met requirements for speed, range, altitude, and a small radar cross-section to evade detection.