Nasa completes preliminary design review of QueSST aircraft design Share 26 June 2017 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.