Those who frequently fly are used to hearing (when their ears aren't plugged) the captain telling the passengers that they've reached their cruising altitude of 36,000 feet.

But, have you ever wondered why jetliners fly so high?  Is there a good reason why you need to spend the majority of your flight FIVE MILES up?

According to Travel and Leisure, the biggest reason is fuel economy.  The air at 36,000 feet is a lot thinner than it is near sea level.  As a result, there is less wind resistance.  So, the plane can fly as fast as it would at a lower altitude without using as much fuel.

Additionally, traveling at that altitude usually puts that plane above birds, drones, helicopters, and small aircraft.  It also lessens the chance of the flight encountering turbulence and, if there is an emergency, it gives the pilots much more time to find a place to land.