https://www.quora.com/Do-[...]s-think-the-earth-is-flat

They had better not, as their navigation over long distances is based on a spherical Earth model. Think about it. If you’re flying from New York to Paris, the path your plane follows over the ground is radically different on a flat Earth from a round one, particularly as measured by a gyroscopic compass.
But, fundamentally, the navigational geography and mathematics that pilots have to master in ground school simply don’t work on a flat Earth.

I can quite confidently say that the answer is no, pilots do not think the earth is flat, they know it is not!
If it were flat we would fly in a constant direction to get from A to B. In fact we fly a great circle which means that our true heading is constantly changing because we are flying over the curve so to speak.
If it were flat then all of the metrology that we study and understand would be incorrect.
If it were flat winds would not behave the way they do.
If it were flat then we wouldn't loose VHF radio communications beyond about 200–250 nautical miles as the station on the ground is hidden by the curvature of the earth (this would be useful!).
If it were flat then sunrise and sunset would occur sulimultainously wherever you were.
If it were flat then sunset would not be ‘delayed’ when flying west at dusk as we ‘chase’ the sun around the globe.
Oh, finally, from 45,000 ft I can see that it is not flat!!!
PS: I would not get in an aeroplane with a pilot who believed the earth was flat. No way!!!
PPS: I know pilots who have circumnavigated the globe. How the hell does that work on a flat-earth model?!!