Oh boy, this has potential. I'll try to put the fire out before it starts.

It's an AIR plane. The frame of reference that matters is the AIR. That is the frame of reference that is moving with the air. Unless it hits you or something else on the ground, the ground frame of reference doesn't affect the plane while it's flying.

The inertia that you talk about is not an absolute quantity. If you are on a bike going 10 mph west and a park flyer doing 15 mph west overtakes you and hits you in the back, you do not feel the effects of 15 mph worth of inertia. You feel the effects of the difference. 5 mph. Make sense?