Originally Posted by
jbjelloid
Yesterday on the 747 flight from JFK to AMS the flight map showed speeds of 1135kph and 707mph as we flew over England. Is that even possible? I was waiting for a sonic boom. Captain did mention 'extreme winds".
Yes, it's possible. No, there won't be a sonic boom.
The speed of sound does not include wind -- if the air in a certain place is moving in a certain direction at 200 km/h, then the speed of sound in that place will be 200km/h faster as well. A plane flying there can exceed "the speed of sound" (in still air) easily by flying within 200km/h of that value. It's not moving faster than the speed of sound in the air around it, but its ground speed is faster than that.
(This is quite unlike the speed of light which is absolute.)
The airshow always shows the ground speed.
Also, a sonic boom wouldn't be heard if you were in the plane even if it did cross the sound barrier -- the boom is heard only outside the plane when the shockwave passes.