When a jet is flying at or above the speed of sound (760 mph), it is expected that a sonic boom and even a shock wave will be observed. AVweb explains the science behind these cool phenomena.
A plane moving through the air close to or beyond the speed of sound causes some unusual visual effects. Air speed increases as it flows over the body of an aircraft. As pressure all around the plane drops, the air cools. As air cools, its ability to hold moisture drops. If there’s enough moisture in the air, a cloud cone behind the aircraft will form. Shock waves are formed by the air that can’t get out of the way fast enough, forming a pressure wave. Humans perceive that pressure wave as sound.