Nice history and understanding shock waves, critical Mach number(speed of airflow goes over the speed of sound) on wings even when a plane is flying below the speed of sound.
#^Critical Mach number - WikipediaIn aerodynamics, the critical Mach number (Mcr or M*) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.[1] At the lower critical Mach number, airflow around the entire aircraft is subsonic. Supersonic aircraft such as Concorde and combat aircraft also...
