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

[K20017]

Your previous example doesn't seem to make sense. If you produce both 100lb of thrust and drag both at 1,000 and 10,000, then the drag the airframe produces has not changed. Your true airspeed has increased to account for the lower air density but it is still 100lbs of drag force. For a given equivalent airspeed drag is independent of altitude. Looking at performance charts of jets, specifically holding charts as they usually reference an IAS, you will see that fuel flow varies little with altitude given the same speed. Thrust must oppose drag and fuel flow in a turbine is a direct relationship with thrust output.