Two subsonic prototypes of planned supersonic commercial aircraft launched by separate start-ups are on track to enter flight test later this year.

Colorado-based Boom Technology has completed wind tunnel tests of a one-third-scale, subsonic prototype, the company announced on January. The start-up now has the data to begin building large structures for the scaled prototype aircraft by year-end.

Last year, Boom announced plans to develop a 45-seat airliner capable of speeds up to Mach 2.2. The design makes no attempt to muffle the sound of the “boom” produced by the supersonic shockwave, so the airliner will be limited to subsonic speed over land. Despite that limitation, Boom’s veteran staff of aerospace engineers believe there is a strong market for an all-business class airliner that can fly above the speed of sound over water.

Separately, Boston-based Spike Aerospace says it is on track to complete first flight of a subsonic, scaled prototype for the Spike S-512 business jet by late summer. A series of larger prototypes will follow, leading to flights by a supersonic demonstrator by the end of 2018, the company said on 23 January. Spike plans to deliver the first aircraft in 2023.

The S-512 is being designed to mask the noise produced by breaking the sound barrier, potentially allowing operators to fly the aircraft over populated areas if the US and European governments lift bans on supersonic flight by non-military aircraft.

Both start-ups are the latest to chase the dream of commercial supersonic travel, since the retirement of the Aerospatial/BAc Concorde fleet in 2003. Billionaire Robert Bass founded Aerion in 2002 and it continues to work towards fielding the AS2 supersonic business jet in 2023. Engine selection for the AS2 is expected in the first half of this year.