This makes no sense at all, the centre of gravity is at the centre of the Earth, thus all objects are pulled to the centre, no matter their position on Earth, or their altitude.
If the Earth is a globe, the plane has to fly flat or its lift and gravity would fall out of equilibrium and it would nose dive.

I still maintain the best test is a circumnavigation of Antarctica. When concluded were you turning left or right?
If traveling the same path on a flat Earth and a Globular Earth around Antarctica, the direction you turn would be oppositional.
Secondly, what was the total distance you traveled?
Flat Earthers claim that Antarctica rings the outside of the Planar Earth, that makes it's circumference enormously bigger than the circumference of a filled Antarctica on a Globular Earth.