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

Being a mile above the ground increases your travel distance by about 1/4000, or 0.025%. This is astoundingly small.

Being a mile above the ground reduces air density by something like 20% so you’re pushing through 20% less air and moving through 0.025% more from extra distance. Extra altitude is clearly the winner.