When shooting moving objects, you need to freeze the movement. This means you need a higher shutterspeed (shorter exposure).
Using the same exposure as with static objects will incur motion blur on the moving object. This can be used to effect, but unless you do so deliberately it is highly annoying.
Yes, this is because fast moving aircraft require faster shutter speeds, which in turn require better light. This applies to all cameras.
Pan smoothly, squeeze the shutter gently and resist the urge to stop panning as you take the shot. I think your camera has the 38-380mm IS lens. That helps.
I've looked at your shots in the database - they are very good.