"As you can see, the unicorns seem to possess a telekinetic ability. We suspect that the winged ponies also have some sort of TK ability as well, which enables them to fly. As you can see, there is simply no way that their wingspan, even in Ponyworld's slightly lower gravity, could support a creature of that size. At least, not without the creature being so light that its mass wouldn't be able to overcome air resistance to allow it to move forward.