I continuously hear the argument that airplanes do not angle their noses down to compensate for a curvature in the earth. Someone even took a level into an airplane and demonstrated that the plane always remained level, and never had to nose-down for the curvature. This is used as definitive proof that the earth is flat.
I disagree with the notion that this is proof of a flat earth.
If you attach an object to a string and spin it around in circles, the object will remain the same distance from the end of the string the entire way around as long as you spin it with constant force. For a moment, let's assume the earth is round and gravity is a real force. In a RE model, the force of gravity is constant (9.8m/s squared). As an airplane flies around the earth and the pilot flies level, the force of gravity would keep the airplane the same distance from the ground without any manual intervention by the pilot. Gravity would pull the airplane around the curve just as the string pulls the attached object around in circles.
Alas, a pilot does not have to fly downward to compensate for earth's curvature, gravity does this for him/her.