cjcampbell wrote

If the car's airspeed indicator said 60 then the speedometer will
indicate 120. But the car would then need to expend the same energy to
accelerate to 60 as it would to accelerate to 120 on a stationary road.


An aircraft would need no additional power to accelerate to 60 on a
treadmill.

To which I'll note that you're on the right track, but remember kinetic
energy varies as velocity squared: it takes 4 times the energy (at non
relativistic velocities) to get to 120 as it does to 60: actually a lot
more than that because windage losses and the like are not linear,
either.