Answer: transonic

AnswerCrossword Clue
TRANSONICHaving Mach speed
TRANSONICOf aeronautical speeds between 600 and 900 MPH.
TRANSONICOf aeronautical speeds.
TRANSONICMoving at 700-780 m.p.h. at sea level
transonicDenoting or relating to speeds close to that of sound
transonicrelating to the range of speeds close to that of sound