This is the first part of a two-part question.
This question is actually related to a question I asked earlier about Ancient Temple Booby Traps Designed for Dragons (link here Ancient temple booby traps designed for dragons)
Now this question deals with the same dragon civilization dealing with their main method of transportation.
Originally I wanted to use old-fashioned sailing ships, but the major problem is that it is noticeably slower than flapping wings and flying to the destination. But after a bit of thought and reading, I came upon an unorthodox solution. Dragons by their nature know that flight is possible, why not make their ship fly too.
Now the real question is how the heck do we get the ship airborne in the first place? Lighter than air gas was out of the question because of the tech level, and the nature of the passengers would turn every vessel into a powder keg waiting to go off. One alternative that I thought might have some merit was to essentially make the ship a hot air balloon.
A dragon crewman stands under the mouth of the balloon and breaths a quick stream of fire up the throat, that fire heats the air inside the balloon, the ship rises. Nice and simple. But even with a lower gravity (0.8 G) and denser atmosphere (1.5 earth standard), I have questions about how well an airship of this type can stay airborne.
So my question is: How feasible is a large airship held aloft by dragon fire breath heated air balloon?