Even at 420mm you must have done a lot of cropping on this shot, yet look how sharp and detailed! This is the first aircraft in flight photo I've seen with the 1Dx, thanks for sharing.
Thank you for your kind comments. The image was not taken at an air show and I was therefore closer than you may expect. You are right though, a small amount of cropping was carried out to position the aircraft in the frame.
As far as the 1dx goes, no complaints at all. It has coped with everything from landscapes to 200mph jet model aircraft. Like the one below.