When shooting aviation, I almost always put my camera on Aperture Priority. This way I can get the depth of field I want, and the camera will meter the shutter speed for me. I can also control the exposure compensation if it's a bright day, or a bright aircraft, and vice versa. The camera will still take care of the shutter speed. On auto mode, the camera does everything itself and you have no leeway with artistic value. Going up or down an exposure stop can have a huge effect on how a picture looks, and even how good the quality is.
It's to each his own, but that's what I do.
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