Thanks Dave! The problem I am having is acquiring initial focus on a military jet flying overhead with the lens at 500mm. The jet swings around through the viewfinder, and I need to half depress the shutter release while the jet is on the center focus point in AF-C. If I catch the jet in the focus point, the camera will focus and track it well. But if I miss, only sky will be in the focus point and the lens will hunt, causing me to lose sight of the jet and miss the shot.
Would Auto Area AF work better in this circumstance, given that the jet is the only subject in a field of blank sky?