Your shot here looks soft.
Like you I will be shooting fast moving subjects (jets) and I am concerned about how sharp this lens can be.
The alternative is a Canon 400mm f5.6 L with a 1.4 TC which is reportedly sharper especially as I will be shooting at the long end most of the time.
Have a look at the Tamron review here - the 600mmm shots are very poor:
https://www.youtube.com/watch?v=1fmMG5jgDwkHow do you find this lens for sharpness at the 600mm end?
I am thinking of getting one for shooting airshows but I've seen it heavily criticised for bad softness near the long end of the zoom.
How is yours for sharpness near the 600mm end?
I will be using it on a 5D3 body.
it is plenty sharp at 600 but it IS sharper at 500mm
there are other reports that say the opposite