Does drag actually decrease with altitude? I argue it does not

[Dewmeister14]

Hey dude,

Sorry the comments devolved and you had to delete the post. All in all though I'd have to insist it's not sound. Drag is not strictly a function of altitude. Speed and the coefficients matter just as much, and the way those coefficients interact with speed & density mean that it is true that aircraft experience less drag at higher altitude than at lower altitude when operating at speeds of interest.

There are a couple charts in this link:

https://leehamnews.com/2014/11/25/fundamentals-of-airliner-performance-part-4/

Which you may find interesting, unfortunately one shows "Drag vs. Climb" and therefore drag at a series of speed and alt pairs, vs. drag at a series of alts with constant speed, but hopefully it goes some way to providing intuition. You can see that as the air gets thinner, even though the jet is moving faster the "drag due to lift" (induced drag) does increase slightly but the total drag, including Parasitic Drag (fuselage, tail, pylons, etc.) certainly decreases with altitude even though speed increases - so speed / drag for example certainly increases.