WTF cloud (Silesia, Poland)

Strange cloud appeared yesterday over Rybnik, Silesia (south Poland).




Officials say there was nothing unusual over this part of the sky, and the clouds are forming behind the planes landing at Katowice - Pyrzowice airport. Its so visible due to the very clean air in this part of Poland.

I personally dunno what to think about it. Can't see a plane, but again I can see it changes direction later on...
What I can tell They really have a clean air over there, despite Silesia is one of the biggest European coal mining regions.

Note this vid was uploaded on YT by TheUkaszPL
Original Link: http://www.youtube.com/watch?v=s_ATdELe5hY&;