I go as simple as possible whenever going to an Airshow or the race track. 1 camera, an all-arround zoom for the static displays, and always my 70-300 AF S tele. It's lighter.
Set as much as I can beforehand, because there is not a lot of time between sets. Shutter speed...propeller planes 1/250-1/400 sec. to provide good prop blur. ISO, as low as you can get away with, given lighting conditions. Jets, I start at 1/1000 sec., but lower works, too, depending on personal steadiness. Helicopters, enough so the main rotor shows rotation, avoiding the look of an insect pinned to a board.
At Airshows, shooting wide open is a possibility, given the distances required for spectators. Getting in position early is advised, but a person might have to deal with the shorter, rude person who arrived later, then tried to rest his tele lens on my shoulder for stability. A light snack is a goodness, as are a hat and sunglasses, too.
If you can get a photo credential, ear protection is advisable. If you wear a photo vest, an extra battery or two, memory card, sunscreen and water won't up the weight much. Know where the First Aid tent is, in case of need. Then....turn off the Electronic Master, and enjoy the show, or...scan the crowd for interesting people to photograph!
I remember in the dim past, a photog with the handle "Desert Rat" who made his 70-200 mm f/2.8 SING!