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

Thinner atmosphere means less air is in the way of the plane (less air resistance).

It also means less climbs/descents over the course of the flight. Each one is more turbulence, and each climb costs more fuel.

It also means less weather. Sure, there’s *really* tall clouds out there, but much of the flight is above the level of most clouds. This also means less turbulence and better fuel efficiency.