Supersonic flight without the sonic booms just edged closer to reality.

NASA announced December 16 that it had approved the final assembly of the X-59 Quiet SuperSonic Transport (QueSST). Built in partnership with Lockheed Martin Corporation, the X-59 QueSST is designed to cruise at a speed of more than 1,500 kph and create a sound about as loud as a car door closing, Lockheed says.

It was the last programmatic hurdle for the plane to clear before officials meet again in late 2020 to approve the airplane’s first flight in 2021.

See the plane in action with this video from Lockheed.