That's indeed what I'm assuming and I also assume it's also to block out the sun.

(Which is in their agenda)

But even if it wasn't what I believe and it's just jet fuel/smog/pollution, it's mostly because people are going back to their home country because they had to escape their country due to inflation or war caused by governments..

There's also several other reasons why I believe it would be the first part, but don't really have the time now to start listing all the things now