Nasa has completed the preliminary design review (PDR) of its Quiet Supersonic Transport (QueSST) aircraft design, thereby achieving a major milestone towards developing a supersonic passenger jet that can travel over land.

QueSST is the initial design stage of Nasa's planned Low Boom Flight Demonstration (LBFD) experimental airplane, which is also called as an X-plane.

The QueSST design can help LBFD aircraft to achieve its mission objectives, which include flying at supersonic speeds, but creating a soft 'thump' instead of a disruptive sonic boom that usually supersonic jets create.

"Our strong partnership with Lockheed Martin helped get us to this point."

The LBFD X-plane will be flown over communities that will help in collection of data necessary for regulators to enable supersonic flight over land across the world.

Nasa teamed up with Lockheed Martin in February last year for the QueSST preliminary design.

In May, a scale model of the QueSST design completed testing in the 8ft x 6ft supersonic wind tunnel at the agency’s Glenn Research Center in Cleveland.

Nasa's commercial supersonic technology project manager for the preliminary design David Richwine said: "Managing a project like this is all about moving from one milestone to the next.

"Our strong partnership with Lockheed Martin helped get us to this point. We're now one step closer to building an actual X-plane."

Following the completion of the PDR, Nasa's project team can commence the process of inviting proposals later this year and awarding a contract by early next year to construct the piloted, single-engine X-plane.

Flight testing of an LBFD X-plane could commence by 2021.

Nasa will soon work with Lockheed on finalising the QueSST preliminary design effort, which comprises a static inlet performance test and a low-speed wind tunnel test at NASA's Langley Research Center in Hampton, Virginia.