I just read through this, and someone wrote the (magnetic) heading changes on a great circle route are so small, they are actually not detectable. That is not true, expecially not when you are flying over great distances (which I do professionally). As a matter of fact they are quite big and very detectable and also a challenge, if you have to calculate your great circle distance on a chart rather than letting the Flight Management Computer do it. Whereas the Flat Earth Map would give you heading changes as well on most great circle routes, they are different to the ones we get flying in real life, which, in turn, are consistent with the mathematical modell of a rotational elipsoid ("the globe"). There is one great circle route on the Flat Earth Map however, that is completely different to the real world navigation, and that is the Equator. In real life, if you fly along the equator, there is no heading and no course change. That is not the case on the Flat Earth Map, where you have significant course changes even over a short distance. (That means you have to turn constantly to maintain the heading.) I brough this up in the thread "Navigation", but no flat earth person replied to it yet.