Best Canon DSLR for Video

I am looking for a camera able to film aircraft in air shows at a distance. Talking with several people I've decided the best way to go is to get a DSLR over a camcorder due to the lens options (telephoto). I'm wondering if anyone has advice on what the best camera might be for this. I'm thinking the Canon 7D or 6D or 7D mark ii. The 7D being the cheapest is the preferred camera but ultimately I want something that will work well with what I need.

Any thoughts? Best Canon DSLR for Video