try and all and see what happens, take a shot with +0.7 and then another with-0.7.
It all depends on sun angle and what part of plane you are focusing on.
If I relate it to bird photography, if the bird is sitting high in a tree above you and I shoot normal metering due to the bright sky the bird will be too dark. Then it pays to overexpose to see the colour of the bird, yes the sky will be over exposed, but the bird is visible.
Sometimes, its a matter of compromise and picking the time of day.
The idea is to have a high enough shutter speed with a large enough depth of field to keep the aircraft in focus.
I personally would use AV mode and keep and eye on shutter speed, if its under 800 or so increase iso. Selecting TV is ok, but I would leave that for specific things like catching a prop or helicopters.
I have twice now spend 9 day down at Avalon airshow working as volunteer, we were driving volunteers, photographers, aircrew and VIP`s around. My shift would finish at 2.00pm and then we were free to do what we wanted. Now with kids I am not prepared to spend the time down there, but was good fun. Mind you, how many planes can you look at for how long, before you get bored.
Meeting the aircrews was interesting, been inside a B52 and C17 Globemaster. The B52 has got the smallest place for the aircrew, it really is a flying fueltank that also can carry bombs.
Being there for the days prior the airshow is good for getting stationary shots as there is so few people around and you can pick the time of day you want to take photos.