Originally Posted by
jerslice
I know this will run, to some degree, contrary to much of the above advice, but there is no need to shoot any higher than f/9 unless you want to - especially when shooting into the sky. If you're shooting side on's you can easily go down to f/4 or even f/2.8 (what do you need the depth of a higher stop for - especially when mixed with compression from a zoom lens?). Quarter angles can easily do f/4 & f/5.6 and still maintain sharpness across the entire aircraft. The only time I shoot above f/7.1 anymore is if I'm panning or the subject is super large or close and has a lot of depth. Otherwise, you're bumping up your ISO or limiting your shutter speed needlessly.
So I guess a simpler way of putting it - I recommend starting your aperture settings at f/7.1 and lower/faster...especially in low-light / cloudy situations where you need shutter speed!