might have seen these but I think its pretty cool, this only happens when they break the sound barrier
just another glitch in the matrix
Pure speculation, but I would imagine that the invisible parts are the actual 'barrier', as in the high density part of each wave (which accumulates amplitude as the plane continues to fly at the rate the wave travels). Then, as the air passes into the low density portion of the waves, cloud would form--as is observed in cabin depressurization on aircraft--as the capacity for humidity drops with the temperature and the water condenses out.
If they were to hold at Mach 1, the cloud would grow as the 'standing' wave got fed more amplitude. The barrier will jam controls if it's sitting on them, which is why so many early supersonic aircraft prototypes crashed (it wasn't until some guy decided to go faster instead of slow down and abort that they found out it was a minor problem).
yeah I was thinking that exact same thing:D