On the face of it this is a useful lens for airshows generally. The range of zoom and the 400mm should cope with most events. However having used this lens for a few years I came to realise that compared with more expensive lenses such as the 300mm f2.8 it is a little soft at 400mm. The 300mm f4 is sharper also and more reasonably priced but is not a zoom of course.
The 300mm f4 and a 70-200 f2.8 (excellent lens) is a better combination for the camera bag.
It is really down to the cash you have spare, the more you pay the better the lens.
Good luck
Phil
http://www.targeta.co.uk