If I tested it and reported back, then what? The deniers would just keep denying, wouldn't they?
Even if I were wrong about this, which I don't believe I am, it would only throw into doubt the map and the measurements of relativity. The shape of the Earth is my interest not flight times. The Earth has been shown to be flat by direct experiment. If speculations regarding other phenomena turn out to be inexact, fundamental Truth has not changed.
I reason deductively from first principles. We know that the Earth is flat due to direct evidence. The way scientists reason is from speculative theory to indirect confirmation of that speculative theory.
True, flat earthers may speculate and theorize and hypothesize from time to time, but the difference between zetetic flat earthers and scientists is that we reason a priori not inductively, speciously and stupidly.