Why do commercial planes fly at 35,000 feet?

Question

Why do commercial planes fly at 35,000 feet?

In: 13

Answer 1

Higher you go, the less thick the air is.

Less thick the air, the less resistance there is (drag).

The less resistance there is, the less thrust(engine power) you need to move at speeds.

The less engine power you need, the less fuel you need to burn to get that power.

The less fuel you need, the cheaper it is for that flight.

Answer 2

Higher you go, the less thick the air is.

Less thick the air, the less resistance there is (drag).

The less resistance there is, the less thrust(engine power) you need to move at speeds.

The less engine power you need, the less fuel you need to burn to get that power.

The less fuel you need, the cheaper it is for that flight.