Why don't airplanes fly at the maximum height?

By Ahnaf Ahmed Prinon | 2025-06-29 03:54:24

Many of us wonder why airplanes don’t fly at maximum height, even though it’s capable of. We know that, flying at a higher altitude means an airplane covers a slightly longer distance than it would at a lower altitude. So, it is very normal for people to want that planes fly higher in the sky so that they reach their destination faster. Yeah, it’s absolutely fine to have such a feeling, but there’s a physics hiding behind it. Let’s discover it in the simplest way.

Well, there’s a popular formula related to pressure, which is,
P = hρg where,

P= pressure
h= depth
ρ= density
g= acceleration due to gravity.

So, we can derive two proportional relations from this equation,

P ∝ h
P ∝ ρ

Now, if planes move at bigger heights, the depth decreases. If the depth decreases, then the atmospheric pressure also decreases. If the pressure is less, then density of air is also less according to the above mentioned laws. Therefore, the air density is less at greater heights from the ground. Here comes the twist!

What does it mean for the air to be less dense? It means that the amount of gases, especially oxygen and nitrogen is less at higher altitudes. So, eventually, there remains a scarcity of oxygen at higher altitudes. Actually, the fuel of jet engines need to be burnt in order to move the airplanes. Now, what is required for burning the fuels. It’s nothing but oxygen, as we know that oxygen participates in combustion reactions to burn something. Thus, due to the shortage of oxygen at higher altitudes, airplanes cannot burn the fuel of their engines and consequently, they can’t fly anymore. Hence, due to the effect of air pressure and density, the planes do not fly at greater heights above the ground.