Boasting a maximum speed of Mach 3.2 and a cruising altitude of over 80,000 feet, the SR-71 “Blackbird” still stands out as one of the most extraordinary achievements in aerospace engineering. With speeds greater than any jet-powered aircraft, the Blackbird’s flight produced tremendous frictional heat. Now Lockheed Martin’s secretive Skunk Works is believed to be developing the SR-72 “Darkstar” and is sure to use many lessons learned in the hypersonic spy plane.