A common mistake a lot of flight photographers make is to clip small part of the subject (usually a wing tip or the ends of the feet). Compositionally, a clipped image is usually less appealing. However all is not lost. If an image is 'cut' (i.e. a significant portion of the wing or feet) is cropped, then you can still end up with a compositionally interesting image.
Technical Specs: Canon 7D, 70-200 f/4 IS @ 200mm, f/4, 1/1000s, ISO 400.