This alone would suggest that it is due to the atmospheric condition. Perhaps they are just con trails. But it is weird how large they are. I have seen several times how they descend from that high altitude and become progressively larger. After a few hours of planes flying above they cover the entire sky.
Discussion
btw I hate the term chemtrails, as it presuposes the conclusion of what we are trying to find out. Whoever say it sounds like a retard.