If I were buy a setup for airshows, I'd go with:
1. A camcorder with a great zoom button
2. A fluid-head tripod
3. FPV glasses
If you don't mind looking like a dork in public, you can see what your camera sees with FPV glasses so that you know you're getting the shot even if it's sunny outside & hard to see the screen. Alternatively, you can also get a Hoodman hood, which is what I use now:
http://hoodmanusa.com/cgi/commerce.cgi?search=action&category=0004
Panasonic has a really nice camera for $920 that has a 25x optical zoom & a 3MOS sensor:
http://www.amazon.com/Panasonic-HC-X...dp/B00AW54Z7C/
Sony also has a great 4K camera out for $2,000 that has a 12x optical zoom with a 1" CMOS sensor:
http://www.amazon.com/Sony-FDR-AX100...dp/B00HNJWVIA/
The nice thing with 4K is that you can crop your image down to 1080p, which means that you don't have to have perfect aim in every shot because you can just cut out a section & still get HD resolution. Panasonic also 50x optical camcorder for $315:
http://www.amazon.com/Panasonic-HC-V.../dp/B00HPZKQ7U
There's also the upcoming Canon SX60 camera for $550, which sports a 65x lens:
http://www.amazon.com/Canon-PowerSho...dp/B00NEWZ8EY/
Alternatively, doesn't the D7100 have HDMI out? You could get one of those little 7" LCD screens off eBay & monitor that way instead - that way you could sit comfortably with the camera & tripod head arm & position the LCD out of the sun & within easy viewing range.