Yeah, I know you're not supposed to be able to use the Nex for airshow pics, but I enjoy doing things that are a bit of a challenge sometimes.
I did cheat a bit. I bought (for around $20) a cheap viewfinder/magnifier thingie. Works great! Sure it is a bit distorted and has CA, so you can't really judge the quality of your photos as well as without the viewer, but for blocking out the sun and seeing your target, it did the job I wanted it to do.
I can never seem to size pics small enough for this forum.
Check 'em out here:http://www.computingbits.com/gallery/airshow2012/airshow2012.htm
I used the Minolta 100-300 APO (non-D), manually focusing and panning with the motion. Failed attempts were mostly due to my focusing abilities or lack thereof. Panning usually works pretty well along with higher shutter speeds.
In the end, I probably would have gotten a few more keepers with a DSLR. Since my Nex has more pixels and better DR than my DSLR, where I did get a good in-focus shot, it's possible that my results are better with the Nex. I'll probably need to print at poster size to find out.
I've gone to airshows for several years now, and upgrading cameras has definitely improved results, but there is a point where you hit diminishing returns.