It cancels out.
False. The question specifically asked about Coriolis force
- that force is tiny, but it's not zero.

The question named "coriolis force" but referred to effects other than
that. The effect alluded to would be there even on an infinite flat
earth which was moving (though not rotating). To this end, I addressed
that first, and to first order, ("short answer"), the motion of the
destination is cancelled out by the (additional) motion of the aircraft
due to the motion of the destination. The =actual= coriolis effect is a
second order effect due to the fact that the earth's motion is a
rotation, which I addressed later.

There are
teeny effects (having to do with orbital mechanics)

This has nothing to do with orbital mechanics, it's just
plain physics - albeit the physics of rotating reference
systems.

Orbital mechanis =is= "plain physics". The effect I was talking about
was the lightening of an object due to its motion around the earth;
taken to an orbital limit the object becomes weightless, but at slower
speeds reduces the amount of lift needed (and thus drag induced).

There was no flaw in the friend's reasoning. He was
absolutely right to ask about the Coriolis effect.

Of course he's right in asking about the coriolis effect, but that's not
the effect he seemed to be referring to.

he asked me about planes against
or with the earth's spin...

He asked why this didn't benefit east to west
plane travel timewise and hurt west to east.

What is commonly called the coriolis effect has to do with apparant
deflection of a flight path due to travelling to a place where the
velocity of the earth (due to rotation) is different. Generally this
means having a north/south component.

If the plane flew faster, the effect would be greater.

The effect you're apparantly referring to (centrifugal "force") would
increase with velocity. However, the effect commonly called the
coriolis effect is more pronounced at slow speeds, where the earth has
more of a chance to spin out from under you.

[presumably you are referring to:]
...The key is that although the frame of reference (the earth's
surface, or the vehicle) is moving, it is not moving with respect to
itself, since by definition, it =is= the frame of reference.

This is all either wrong or irrelevant to the question.

The question asked and the underlying misunderstanding are different. I
attempted to address them both. And what I said is =not= wrong. You
may be confusing "moving with" with "accelerating with respect to".

It's a good thing I'm not Mx.

Jose
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.