I am less than convinced that dragons use no magic for flying. We know that they weigh up to 40 tons for the battle dragons (HHNF: Fort Salby would have to hold in the face of 30 to 40 ton battle dragons attacking), and that transports are larger. We know from the snippets that transports can haul up to 15 tons with no external assistance, and up to 60 with levitation accumulators (thus, the accumulators dragons can carry can hold up to 45 tons, though that may be many working together). We also know that battle dragons can sometimes take off on their tails from a clearing, and that smaller transports like Windclaw can take off (if barely) along a stream in a heavily forested universe. And dragons fly by flapping their wings, not through wind shape and speed. It's possible they coast at high speed, but 100 mph is possible only in very small airplanes (Cessna single and double person airplanes are 63 mph according to Wikipedia; jetliners are 150-180 mph for takeoff speed). The heavier they get, the faster they have to go. And dragons start off much slower than that.
Putting together their sheer weight, the fact that they fly like birds at least at takeoff, and the fact that a transport's wingspan is smaller than that of an open stream (not a river), I can't see how they could possibly have wings large enough for their weight. Sturdy enough for the weight is dubious but maybe possible given genetic engineering, but if Arcanan laws of physics are remotely like ours, there's no way around the need for enormous wing area to match the enormous weight.
In addition, we know that battle dragons at least are spell accumulators (Gadrial told Shaylar so) to power their breath weapons. We don't know one way or the other about transports without breath weapons, but it seems logical that if you can build that into one type of dragon and include the equivalent of a complicated spell (to make the breath weapons), you should be able to build that into transports with another spell (levitation). It's far from impossible that dragons already had that ability before Mythalans made them into weapons, though we have no evidence either way.
Obviously, whatever levitation spells might be built into dragons aren't enough to hold their full weight. Indeed, in HHNF we learned that spells to hold them in a hover don't last that long, though I don't think we got a duration. But such spells could certainly reduce their weight, also reducing the needed wingspan and wing toughness, not to mention the effort needed to fly. So personally, I suspect they have been spell accumulators since they were transports and use the magic for levitation, but it's purely a supposition right now.
If I remember the interview correctly, Weber said that the physics is significantly different. He said Sharonian physics was Newtonian, with an infinite speed of light. Given that the human eye absolutely requires light to move at different speeds in different mediums, I'm not sure how he intends to make that work.
And I found the link:
https://www.youtube.com/watch?v=jCueWzQCMHk&feature=youtu.be It was in this thread
http://forums.davidweber.net/viewtopic.php?f=6&t=6077 and the part about the multiverse is supposed to start at 1.54.56. I haven't had the time to go back and re-watch it, do I'm still operating on memory.
