You're not getting it are you, are you a moron?
Forget about a globe, OK, forget it.
A plane flies from Newcastle to London or someone drives that journey, the plane or car will register x miles, the same vehicle does the same to Portugal (which I've drove) nobody alters the mileometers on planes or cars depending on where they are going or in which hemisphere, keep extending that further, quantas may fly between 2 destinations in the southern hemisphere, they may go from southern to northern using the same plane, they don't alter the plane and the way they measure the miles, we know how far places are actually apart on our world no matter what shape, you say its flat so nothing to take into account or asjust in your world.
So why are the distances actually travelled and measured incorrect to you?
Or as I say do you have an alternative flat earth list of miles between cities? You must have surely if you know how to map it, pop them up?