Post 3
4:35
Relative humidity at high altitude.  Yes there is almost no water at high altitude.  That’s why your throat gets dry on long flights.  The air, on an absolute basis, is 10x drier than desert air.  Where does the water come from?  Fuel.  That’s the main exhaust product of burning hydrocarbons.  A jet engine is spewing THOUSANDS OF POUNDS OF WATER PER HOUR into the atmosphere.  Creating clouds.  Mic drop.