Airshow lens

I’ve been to Oshkosh at least three times, but this was back in the film days. I used a 400mm at F8 which provided sufficient reach and light in bright sunshine. I would try the lenses you have. Assuming your 70-300 is the USM IS model, it should be fine because it will provide you with 480mm equivalent.  I have owned two of these 70-300 IS USM lenses, and both needed to be at F8 when used a 300mm to be sharp. Use F8 and your shots will be sharp, hopefully the sun will award you good lighting.

The 100-400 would be an excellent lens to.

The Oshkosh air show is a wonderful experience. The people that spend the whole week there really get the best of what it has to offer. You might want to spend some time just to enjoy the event. I was lucky enough to see in flight and very close up, the SR71 Blackbird and also talk to the pilot that flew the Tomcats when filming the Top Gun movie.  Oshkosh provides a nice bonus of having the afternoon sun at your back. The lower the sun, the more impressive your shots will be. Be prepared to be a long way from your car. An interesting note, is that back then, Canon provided a high raised platform with about a dozen telephoto “L” lenses solidly mounted on heads for complimentary use.

Have Fun

Ken