Many of us have probably wondered why planes can’t fly higher than they do now. Well, we have the answers to that! There are three key reasons for this:
Jet airplane engines are designed to run at peak efficiency with a specific amount of oxygen. In order to match that oxygen level, the plane must generally fly within that 30 to 40 thousand foot window. At that altitude, you get the most thrust possible for every drop of jet fuel.
2. AIR DENSITY
The higher the altitude is, the thinner (less dense) the air gets. With less air in the way there is less friction on an airplane. Travelling in the thin air requires much less energy in comparison to thicker air levels. At higher altitudes there is less weather differentiation which causes turbulence. If you have ever experienced turbulence you know that it’s usually not a pleasant experience.
The third reason is air temperature! With an increasing altitude, it gets colder, and the average temperature at 38000 ft. is around -54 (-65 F). Colder air means that the engine will run more efficiently.