I've shot two airshows but only one with a dslr.
For the show, I shot in M. I didn't use Av or Tv because I don't want the background influencing the exposure. You're gonna take shots tracking planes across various backgrounds: bright sky, cloudy sky, mountains etc.. In Av or Tv your exposures will vary wildly.
If the plane is white or unpainted aluminum you may have to stop down or speed up the shutter. If it is black you''ll have to expose more. Basically find a middle ground and adjust it a little up or down depending on the subject.
I shot with a 70-200 f/2.8L IS with 2x TC on a 20D. 400mm is just about perfect for show center but short for shots at the far ends of the show. The 70-200 with a 1.4 will probably be just a little short except for show center.
IS in pan mode can be useful. Hand hold. No need for monopod or tripod.
I'd keep shutter speeds for jets above 1/1000 and as high as possible. For props I think the best is around 1/250 and helos is 1/160 for best prop blur.
ISO 200-400 is probably where you'll need to be to keep high shutter speeds.
It's good to have the aperture relatively high to maximize DOF. f/8 to f/16 but balance this with the shutter and ISO. You could probably go to ISO 800 to keep high shutter speeds and the aperture stopped down if it's overcast.