Here I will do some equipment recommendations, for separate scenarios which I had used and I'm still using (Amazon-affiliate-links behind the pictures):
The 7D Mark II is equipped with 100-400mm lens for everything up in the air. Depends on the light condition and the distance to the planes/ helicopters if it's with extender or not. The 70D is equipped with the 16-35mm lens for anything on the taxiways. Sometimes I switch the lens to 24-70mm, depends on the distance to the taxiway and size of the plane. The 600D is equipped with the 10-22mm lens for splits.
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