What is Prandtl–Glauert Singularity you may ask?
"The Prandtl–Glauert singularity is the prediction by the Prandtl–Glauert transformation that infinite
pressure conditions would be experienced by an aircraft as it approaches the speed of sound.
Because it is invalid to apply the transformation at these speeds, the predicted singularity does not emerge.
This is related to the early 20th century misconception of the impenetrability of the sound barrier."
[link to en.wikipedia.org]

Can someone embed some of these pictures (preferably pictures 6 and 7)?
[link to www.businessinsider.com]