Sound Barrier

As the speed of early aircraft gradually increased there eventually became an awareness during the 1940's, that strange things were occurring at around 500mph. Many later WW2 fighter aircraft were reported to become dangerously uncontrollable in high-speed power dives. Pilot's and aircraft designers were beginning to encounter the sound barrier. We now realize it to be a phenomenon that occurs when the speed of sound is reached and air compressibility demands additional power to break through it