Okay, this is getting more serious than I intended, was just a joke.
But the way, flying south would prove/disprove the theory
RE - you take off, turn the plane due south. Do not touch the controls until you pass over the south pole and keep coming up the other side. In this scenario, the curve you travel is under the belly of the plane.
FE - you take off, turn the plane due south. Do not touch the controls. You will eventually come to the ice wall (or the guards who protect it). If you were to travel in a curve, you would need to bank the aircraft in which case the curve is under the wing, not the belly.