Lockheed Martin Corp.’s Skunk Works facility has started producing the first parts for the X-59 quiet supersonic technology aircraft. The Skunk Works, in Palmdale, is building the aircraft to make it possible for supersonic commercial flights over land resulting in a sonic boom that is as loud as a car door slamming. In April, NASA chose Lockheed Martin, in Bethesda, Md., to design, build and test the X-59, also known as the Low Boom Flight Demonstrator. Peter Iosifidis, program manager for the Low Boom Flight Demonstrator at Skunk Works, said that the long, slender design of the aircraft is the key to achieving a low sonic boom. “As we enter into the manufacturing phase, the aircraft structure begins to take shape, bringing us one step closer to enabling supersonic travel for passengers around the world,” Iosifidis said in a statement. The X-59, designed to cruise at 55,000 feet at a speed of about 940 miles per hour, will have its first flight in 2021.