To add to your last paragraph for folks who find this surprising: If you take a airplane and let the area of the wings go to infinity while taking their wing ma

To add to your last paragraph for folks who find this surprising: If you take a airplane and let the area of the wings go to infinity while taking their wing mass and thickness to zero, the vehicle would expend arbitrarily little energy maintaining altitude; it's basically a giant, extremely slowly falling parachute. Real-world wings do not achieve this of course, but not nearly as much energy needs to be expended compared during cruise as (say) simply hovering by pointing the engine at the ground (if your engine was even powerful enough to do that).