system
Given the following post, respond as if you're commenting on Reddit:
human
Do the control surfaces on long distance flights have to be trimmed slightly downwards to compensate for the curvature of the earth?
gpt
No.

There are four forces acting on an aircraft: Thrust from the engines, drag from the air, lift from pushing air down and weight from gravity.

We trim an aircraft so that the lift and the weight balance out and the aircraft remains in a steady attitude relative to the horizon.

As we fly over the curved Earth, the plane remains trimmed so that "Down" is in the same direction. We don't need to adjust the control surfaces for the plane to follow the curve.