In the words of those who have passed ... 2020 edition, part 2 by Egantx7

Question 18

Sure. I knew the laws of nature, that sound travels at some 760 miles an hour at sea level and some 660 miles an hour at 35,000 feet higher. I also knew we had buffeting problems because of shock waves because I experienced those in air combat, you know, in World War II, when I was flying Mustangs over Germany. I also experienced it in the early jets, the P-80s and P-84s. I knew exactly what the problem was.

Interview with Terry Gross of Byline, 1988

Chuck Yeager (first pilot to break the sound barrier)