Shockwave Formation in Transonic Flight on Airliner

This video captured on an E175 passenger airliner (an iPhone was used - apologies for the quality!). This shockwave formed at the front of the engine nacelle. You can actually see multiple shockwaves!

Here is the explanation that us dumb pilots learn: When an airplane travels less than the speed of sound, the air ahead of it actually begins to flow out of the way before the plane reaches it. These airliners themselves never reach the speed of sound (they get about 80% of the way there), but air particles flowing around certain parts of the airplane may get much closer.

As the airplane catches up to its own pressure waves, the air ahead of it receives no warning of the plane’s approach. Air particles begin to "stack up", creating a shock wave. This is what you are seeing here.