The Blackbird (Lockheed Martin SR-71) flew in 1976 and took the distance between 
New York and London for 2 hours, which means that the aircraft developed 
top speed above Mach 3 (above 1000 m/s or 3600 km/h).
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Now Lockheed Martin develops a successor of the Blackbird indexed SR-72 at the Skunk Works facility. Skunk Works is a nickname for the Advanced Development Program (ADP) of Lockheed Martin. ADP stands behind the SR-71 and other significant projects such as F-117 Nighthawk, F-22 Raptor, U-2 and F-35 Lightning II.
It is expected that SR-72 will reach top speed of Mach 6, or 6 times faster than the sound, and it will be unmanned. If everything goes smooth along the development process, demonstrator vehicle will be ready in 2018 and fully operational in 2030.
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Brad Leland is a program manager at Lockheed Martin, he said: “Hypersonic aircraft, coupled with hypersonic missiles, could penetrate denied airspace and strike at nearly any location across a continent in less than an hour. Speed is the next aviation advancement to counter emerging threats in the next several decades. The technology would be a game-changer in theater, similar to how stealth is changing the battlespace today.”