The Cold War locked the United States and Soviet Union into a tense struggle for global influence and control. The first purpose-built American spy plane to fly over the Soviet Union was the Lockheed U-2. Neither fast nor stealthy, the U-2’s tactical advantage was that it could supposedly fly above soviet radar and air defenses. Yet even before the U-2 began surveillance missions, there were already plans for the next generation of spy plane. The need for a U-2 successor became more pressing as Soviet radars had tracked the U-2 since the very first reconnaissance flight. In 1960, a Soviet surface to air missile downed a U-2 deep within soviet airspace, heightening tensions between the two Cold War rivals. If America was to continue vital reconnaissance missions over the Soviet Union, it would need an aircraft with a combination of incredible speed, altitude and stealth. In 1959, the CIA chose Lockheed over rival Convair to build the next generation of spy plane. Lockheed’s highly classified spy plane would be known as the A-12. Originally designed for the CIA for reconnaissance, the A-12 was also developed as an interceptor prototype, along with a variant that could launch an unmanned reconnaissance drone. The SR-71 Blackbird, a later variant developed for the Air Force would go on to serve for decades while the other variants were quickly retired. Nearly 60 years after their first flight, the SR-71 and its A-12 successors remain the fastest air breathing jets to ever fly. Lockheed’s engineers had to innovate many aspects of the aircraft from unique engine characteristics, stealth features, to the extensive use of titanium for the first time in an aircraft. For years, the SR-71 Blackbirds were practically invulnerable, being able to outfly and out climb any threat, but by 1980s, Mig-31s and a new of generation of surface to air missiles began to erode the aircraft’s impunity. The SR-71 Blackbirds were finally retired from service in 1998. These reconnaissance aircraft were enormously expensive to operate and politics and infighting for defense budgets eventually had the SR-71s days numbered. Advances in spy satellites, aerial drones and the SR-71’s inability to deliver surveillance data in real time, diminished some of the plane’s utility.