Originally Posted by
Zaphod Beblebrox
the stalling AOA remains constant for a given airfoil.
...
Since ρ0 is constant, indicated stall speed will not change as altitude changes.
This is the exact bit that I mentioned earlier, that falls under the "lies told to children" category.
The stall AOA decreases with very high altitude, and the IAS stall speed increases.
Altitude-IAS graph of U2