Nice pictures there Chris, but it does show that for those types of shots you can't beat length!
I've been there with my 55-300mm and still found it lacking for some shots, although you do need shorter lengths for some (display teams and the like).
@mscott, with my (limited) experience of some UK airshows, RIAT has to be the biggest in all respects - size, number of aircraft (both on the ground and flying), display time and oh yes, the hordes of people
Get to the area much after 07:00 in the morning and see how the queues are already forming
I do find some of the smaller displays, such as Kemble and RNAS Yeovilton to be better in some ways - more intimate, easier to get around, find a reasonable spot to take pictures and the like, but at the end of the day, RIAT has got it all and I will be going again.