The reason that explanation did not do the trick is because it simply
is not true. You don't need more power at higher altitude. You need
less power (for the same performance) because the air has less
resistance. Your non-pilot was correct.

Think about it. Your engine power (normally aspirated) drops with
altitude. But the airplane moves faster despite the power drop. If you
can maintain constant power (turbo charging), you get better and
better performance with altitude.




On Feb 2, 6:51 am, "xerj" wrote:
I was trying to explain to a non-pilot why increased power is required with
altitude. She said "isn't the air thinner up there so there isn't as much
resistance?" I said "yes, but the plane needs to fly fast enough for the air
over the wings to feel like it does down low. So the speed required goes up
you get higher. More speed need more power."

This didn't really do the trick.

Can someone think of a better way of putting it without resorting to
mathematics and an explanation of IAS and TAS?

TIA