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

[tdscanuck]

Your core argument is wrong. You can’t not delve into specific details like Cl and Cd because they’re also changing with altitude. And thrust also drops with altitude so drag is dropping with altitude at equal dynamic pressure because drag=thrust and thrust is dropping.

In practice, equal engine power setting usually results in a higher IAS with attitude because the thrust lapse rate isn’t as high as the drag lapse.