Quote Originally Posted by ScottyDsntKnow View Post
I like to go with the Flight of Dragons theory of dragonflight. They have a set of very hard teeth that can grind up limestone. They grind this limestone up and swallow it into a crop or a second stomach of sorts. There it is broken down into Hydrogen. This serves 2 purposes. ....
Unfortunately, limestone is mostly calcium carbonate (CaCO3). Stomach acid is mostly hydrochloric acid (HCl). Mixing acid and CaCO3 produces carbon dioxide, water and calcium chloride. No hydrogen. Zinc metal and hydrochloric acid would react to produce hydrogen gas.

A Boeing 747 is 70 m long with an interior cabin width of just over 6 m and an empty weight of 162 tonnes. That seems a bit excessive to me. Scrooge McDuck's money bin might not hold quite enough treasure to cover a dragon that big. The white dragon of Pern was about the size of a horse. But he was a dwarf specimen. Seems to me that a more realistic range would be somewhere between the size of an elephant (Asian elephants--2 to 3 m from shoulder to toe and 2 to 5 tonnes in weight) and a good sized sauropod dinosaur such as the Apatosaurus (formerly Brontosaurus), which was 21-27 m long, 3-4.6 m tall at the hips, and 30-35 tonnes in weight. But I can't visualize a physical mechanism that would let a creature in that size range actually get off the ground.

Sauropod dinosaurs had a pretty good sized "brain" in the spinal cord at the hips. We might postulate that the hindquarters brain had a levitation function built into it. And the wings were for maneuvering. Dragons are fantasy creatures, so why not a fantasy flight mechanism?