Why did it seem like only Voldemort and Snape could fly?
During the asking and answering of my question about people flying, one point has come up: Both Voldemort and Snape flew, seemingly on their own.
However, in Quidditch Through the Ages, by J. K. Rowling (in other words, not fanfic or written as part of the franchise, but by the author herself), it specifically states that there is no known spell that can make humans fly.
Which leaves the question: How did Voldemort and Snape fly? Did they have something in their clothes that flew like a broom? Did they make long underwear they could put on under their clothes and enchant that? Just how did they fly?