The FAQ says you can circumnavigate the Earth by flying East or West, and arrive where you started your trip. Now, the further South you go in FET, the longer your trip will be. So, you take two planes, put one at 50* North and one a 50* South, at the same longitude; then, you send them both West. The North plane should arrive at it's starting point long before the Southern plane arrives at its own. But...they'll get there at about the same time. Explain pl0x.
Now, I haven't done this experiment, I'm just going to say that so you don't have to ask. But planes in the Southern hemisphere don't carry 4 times the fuel that planes in the Northern hemisphere-disc do.