You can do this same sort of thing in the Northern Hemisphere. It just gets more obvious the further you go south.

For example, check a direct flight from LA to Seoul. On a Gleason map (the most common flat earth map, though there are a few others), flights between those two should be going well over Alaska and parts of Russia. On a great circle route, they barely go over the Aleutians and don't go into Russian airspace at all. Guess which one flights actually use?