That's a good point. For a stationary observer sitting on the ground it would roughly seem that, in the airplane case, you increase your speed from 100s mph to `100s + ε mph`, while for the home case from 0 mph to ε mph. So that seems like a counterexample to what I described as common kinetic experience.

I think the issue here is that, in order to move, you apply force to the floor of the airplane. Because the airplane has huge mass and your mass and relative speed are minuscule, there is (probably) no perceivable effect on the airplane's motion. So you increase your kinetic energy by the same amount in both cases while expending the same amount of (chemical) energy, but in the airplane case, the kinetic energy of the airplane (just the airplane, without you) decreases (by a miniscule amount compared to its actual kinetic energy, but still).

When you get up from a seat and walk a few steps you are already doing that on something that is hurtling down space. We don’t notice that our planet moves a lot, because we can’t really see the movement in our reference frame. If you were on a plane without any windows, no turbulence and no sound cues from the engine, you wouldn’t know when getting up from your plane seat that you are in a moving object either.

Acceleration is a real force that we can feel. But once moving at a constant speed, physics dictates that it’s all the same. That’s also why you can throw a tennis ball up on a plane and not have it fly backwards immediately smacking into the person behind you.

In the reference frame of you and the aircraft, you are not moving at all and neither is the plane. In the reference frame of the ground you and the plane are moving.

I guess Galileo came up with it first:

https://en.wikipedia.org/wiki/Galilean_invariance

you are still moving against reference frame (floor) that is at speed 0.

and also pushing that reference frame down when moving up

If you're talking about intuitions, you have no firsthand intuitions about lifting effort decreasing with distance to the Earth. We can intuit about constant gravity, and the math of constant gravity works fine for this description.

And while the real situation at scale is more complicated, the math is going to come out to the same answer, albeit with extra terms muddying everything up.

If someone says that something true can be illustrated intuitively with a thought experiment, "sure, but what if we take that to a scale where our intuitions fail" is a sort of odd place to take the discussion unless you're genuinely curious how the math is going to shake out.

On earth, it just about is... you haven't scaled up enough. Low earth orbit doesn't have much less gravity, it's just that there's no air resistance so you can move fast enough sideways so that you don't run into the earth. Hence orbit and not just floating.

But more to the point the kinetic energy here is being turned into gravitational potential energy. If you move to a place with a weaker gradient in gravitational potential of course the same amount of kinetic energy moves you farther up.

What intuitive understanding do you have of moving furniture up 10,000 floors? None.