For ground-based images I use a Fuji 2800... 6x optical zoom.
Digital cameras have an annoying lag between pushing the shutter button and actually getting the image.
For action pictures, this means the subject might not even be in the image when the camera does its thing.
To get around this, I've epoxied a sighting tube on the upper left of the camera body, which I use to follow the subject while the camera is thinking..
And there's a 4-shot burst mode at maximum resolution which helps get a good image.
Samples..
The takeoff shot, the closeup and the real closeup are all taken while flying the model... all at 6x zoom
The SP2H shows what happens when the pan rate changes .. almost got the whole thing but..