I am curious about any reference in the books. Is there any suggestion in any canon or semi-canon sources about how long it takes to reach destination B from destination A on a dragon's back?

I am also curious about how long can a dragon keep flying, if it is referred to in the canon and semi-canon sources.

EDIT: I am actually more interested in the sprint speed of dragons. Here we see Drogon causes a very high pressure underneath.

I think we can get the sprint speed using water viscosity, water depth and wavelength of water. However, I am not well versed with fluid dynamics, so I wanted to start from here.