I'm a physicist who was amused by the argument in the comments of this question about gravity. The correct answer about the affect of the accelerating reference frame of the plane on the apparent gravity depends on how the airliner's speed is measured.
I know very little about practical aviation.
When I'm on a trans-Atlantic flight moving 900 km/hr, with respect to what am I moving? Is that my speed relative to the ground (which is also moving)? relative to the local atmosphere (which could be additionally moving due to wind)? relative to some imaginary, absolute grid hovering above the Earth's surface? relative to the "fixed stars"?
This is probably a duplicate, but I can't seem to find the right search terms...