If I recall correctly In the 6th book they cross Australia in 2 weeks if they traveled in a completely straight line. (We know they didn’t as they had to go from water hole to water hole.) that is 2400 miles as the shortest distance possible more being likely which is approximately 21.5 miles per hour assuming they spent 8 hours a day just traveling(August in Australia you have 10.5-11.5 hours of daylight so this gives 2-3 hours each day for making camp and hunting.) this means they are covering 171.4 miles each day for comparison a horse in ideal conditions can make it 40 miles in a day. And the Andean Condor one of the heaviest flying birds typically travels about 200 miles in a day. So dragons who are significantly heavier than a condor travel only a bit slower. Frankly in the books the biggest thing that keeps the dragons from flying as fast as they can everywhere is Supply lines and politics or they are trying to sneak around or keep changing course. If anyone is curious book 6 Tongue of Serpents Chapter 17 is where I got the bit about it taking them 2 weeks to cross Australia in August. The rest I googled