Relating to or flying at a speed or speeds less than that of sound.
- ‘The aircraft's fixed-wing profile with large wing leading edge root extensions gives good manoeuvrability and control at subsonic speed including manoeuvres at high angles of attack.’
- ‘Once the vehicle returns to the lower atmosphere and drops to subsonic speeds, the jet engines will reignite for a powered landing back at the spaceport.’
- ‘The plane, with three pilots and a number of other cabin crew, then turned round and headed back to Heathrow, flying at subsonic speed and landing safely at 2.06 pm.’
- ‘The variable sweep wings are set at 20° for take-off, loitering and landing, and automatically change to a maximum sweep of 68°, which reduces drag for high subsonic to supersonic speeds.’
- ‘To improve the aircraft's longitudinal stability, and to avert stall at steep angles and subsonic speed, there are two shallow upper-surface fences on each wing.’