Last week, NASA cleared the way for final assembly of the $248 million X-59 Quiet Supersonic Technology (QueSST) demonstration aircraft. The X-59 is being developed by Lockheed Martin’s Skunk Works in Palmdale, California, and is part of NASA’s integrated aviation systems program’s low-boom flight demonstration project.

The aircraft is shaped to mitigate the loudness of sonic booms reaching the ground and will be flown over select U.S. cities to gather data from sensors and people on the ground. Data gathered from the flights will be used to help regulators establish new rules to enable commercial supersonic air travel over land. Supersonic flight over land by civil aircraft is currently banned in the U.S. and much of the rest of the world. Aircraft manufacturers have repeatedly said establishing those regulations is the key to enabling development of a new generation of supersonic aircraft for business aviation and airlines.

Final X-59 assembly and systems integration, including the cockpit external visibility system, is slated for 2020, with first flight expected in 2021. Bob Pearce, NASA associate administrator for aeronautics, said the X-59 is on schedule and on track. “We have everything in place to continue this historic research mission for the nation’s air-traveling public,” he said.