dismissed the topic myself a long time.

but now i am looking into it.

the best proof for me is the gyroscope.

its a mechanical device which shows the tilt of an airplane for example.

if you would fly around a curve / globe the gyroscope would show the tilt because it does NOT adjust by gravity.

its a little technical and some say it adjusts with gravity

but this is just wrong, because then it would also adjust when you start to fly a 1 degree angle.