how do dragons fly? (Spoilers all books to end DH)

[assasin]

But they are too big to fly. There is a lot about dragons we dont know. For all we know their magic makes them lighter. It would have to help them in some way. Just not cause them to levitate.

The average dragon is as big as a ship. The biggest pterasoar [flying reptiles] were [dont know the exact size] at most as big as a truck. A small one. Which is nowhere near the size of a ship. And thats when the dragons are new out of their cases. They need some advantage caused by magic. Its the only logical explanation. Well that and sacks full of helium. But I doubt thats the case.