[kergonath]

It does not really, at least not directly. What matters is relative velocity compared to the starting and final locations, and relative to the air around the aircraft. It just happens that there are very powerful atmospheric currents that go west to east (those are due to the earth’s rotation, among others phenomena).

So, when flying towards the east, catching these currents can significantly reduce flying time. When flying towards the west, we want to avoid them by flying below or elsewhere.

[prmph]

Thanks for this explanation; quite interesting.

But it still seems to me that there might be a gravitational/inertial effects at play as well. At a (hypothetical) infinite altitude, it can no longer be said the the plane is moving perfectly in lock-step with the gravity/rotational acceleration of the earth. This implies the inertia of the plane relative to the rotation of the earth still has an effect at lower altitudes.

The effect might be tiny, but would be interesting to learn more about it nonetheless.

[BlueTemplar]

What gravity/rotational acceleration ?

Something like this does exist under general relativity :

https://en.m.wikipedia.org/wiki/Frame-dragging

However,

> This does not happen in Newtonian mechanics for which the gravitational field of a body depends only on its mass, not on its rotation.

[prmph]

Yes frame-dragging seems to be the name of the concept I was thinking of. Cool.