Show Information (From 2018)NASA has taken another step toward re-introducing supersonic flight with the award Tuesday of a contract for the design, build and testing of a supersonic aircraft that reduces a sonic boom to a gentle thump. Lockheed Martin Aeronautics Company of Palmdale, California, was selected for the Low-Boom Flight Demonstrator contract valued at $247.5 million with work going through Dec. 31, 2021. Under this contract, Lockheed Martin will complete the design and fabrication of an experimental aircraft, known as an X-plane, which will cruise at 55,000 feet at a speed of about 940 mph and, instead of a sonic boom, create a sound only about as loud as a car door closing in the distance equivalent to approximately 75 Perceived Level decibel (PLdB).