I'm not sure anyones suggesting they couldn't fly at all, just that some researchers propose what they were capable was closer to jumping off trees or hills and gliding to the ground, rather than launching from flat ground and flapping their way across continents.
Though there's at least one guy who ran some calculations for Quetzalcoatl's probable aerodynamics and came up with numbers suggesting it could fly ~10,000 miles. Other people criticise that saying it only takes into account estimates of bone/wing structure and body weight, and ignores energy requirements which reptilian metabolic possibly cannot provide.
I hope they're wrong. I desperately want to believe that there once existed 35 foot wingspan "dragons" which were capable of trans continental flight :-)
(Warm-blooded reptiles sort of still exist. https://www.newscientist.com/article/2074982-first-warm-bloo...: “The surprise came when the lizards reached the reproductive time of the year, from September to December. During the cold early hours of the morning in that season, their breathing and heart rates rose and their temperatures reached as much as 10 °C above those of their burrows”)
Soaring birds get most of their energy from currents of rising air, not flapping their wings. So it’s plausible it did a lot of soaring over land, assuming it could get in the air under its own power. Human-built gliders can fly thousands of kilometers in one go, admittedly uncomfortably and geographically constrained.
But easily hundreds of kilometers on a day with good conditions, with a good degree of navigational freedom.
Though there's at least one guy who ran some calculations for Quetzalcoatl's probable aerodynamics and came up with numbers suggesting it could fly ~10,000 miles. Other people criticise that saying it only takes into account estimates of bone/wing structure and body weight, and ignores energy requirements which reptilian metabolic possibly cannot provide.
I hope they're wrong. I desperately want to believe that there once existed 35 foot wingspan "dragons" which were capable of trans continental flight :-)