See them round here quite a bit.
I was on my way down to Osoyos, I stopped to regas at Hope. The airport there is in a valley maybe a mile or mile anda half wide with two or three others branching off. While I was filling up a chap rushed over from the gliding club and said they were going to close the airport due to local firefighting so I had about ten minutes to get out. Just then a Mars flew out of a really narrow branch valley at about a thousand feet and disappeared over the hill towards the lake. It is big. I was on my way in about three minutes.