Quote from pspr:
At around 20,000 feet the speed of sound is 660 MPH. Most airliners have a cruising speed between 450 and 500 MPH. It's not likely you were flying at 650 MPH at 39,000 feet.
Well, maybe the gps thingy on the plane was wrong, but it definitely said 650 mph, and we were at 38000 plus feet, the temp of the air was -70 F. It was fascinating.
