Hurricane Fluttershy had some Twilight technobabble. The weird thing is that the technobabble was actually sensical. "This is an anemometer. It measures your accelerative velocity and translates it into wing power, thus gauging your cumulative H2O anti-gravitational potential."

Pegasi apparently use the moisture in the air to fly instead of pushing all the air like real winged creatures. That is actually really smart. If their magic pushes up against the sparse number of H2O molecules normally in the air and lets them fly easily, wouldn't that make clouds pretty much a solid surface to them? I feel kind of dumb for not noticing that before. I guess winged animals do the same thing in the MLP universe, since they can chill out on clouds too.

It also explains how they can use a tornado as a reverse funnel. It's not just the wind, it's their magic pushing the water into the pony-free centre, letting it float freely and making the water shoot up into Cloudsdale through the actual wind force. Otherwise, the water would all be in the same space as the ponies, there would be no shooting action and it wouldn't be very nice to fly in.

Hmmm, now I wonder how dry it has to be to make flying impossible.