Why do planes fly at high altitude even across the oceans, when flying at lower altitudes require covering a shorter distance?

Question

Why do planes fly at high altitude even across the oceans, when flying at lower altitudes require covering a shorter distance?

In: Engineering

Answer 1

As others have said, the air is thinner and results in less aerodynamic drag. Drag increases approximately with the square (in most, but not all cases- drag is a highly complex calculation that can vary based on many environmental and situational variables) of velocity so, as you can imagine, if you reduce the density of the medium by ~20% you will massively decrease the drag when the object is traveling through that thinner air at hundreds of mph.