Matt Whiting wrote:
Because when you leave the earth you are traveling the same relative
speed as the earth as is the atmosphere in which you are traveling.

Right. I think Xerj was confused because he was talking Coriolis effect
and someone asked him why flying against the earth's spin isn't faster.
The simple answer to that question is Newton's first law of inertia.

The second question is how come it's faster to fly with the earth's
spin then? The answer to that is that winds generally blow from west to
east in the northern hemisphere... which is partially due to the
Coriolis effect (as well as heating patterns). But that's an indirect
effect.