In Which Layer Jet Aircrafts Fly?

Commercial jet aircraft fly in the lower stratosphere to avoid the turbulence which is common in the troposphere below. The stratosphere is very dry; air there contains little water vapor. Because of this, few clouds are found in this layer; almost all clouds occur in the lower, more humid troposphere.

Where do planes and jets fly?

Planes are usually flying in the stratosphere, which is the second major layer of the earth's atmosphere. The reasons why they do this are very practical and not that difficult to understand.

Why do not jet aircrafts fly in the troposphere?

The troposphere is the densest part of the atmosphere where 75 - 80% of the atmospheric mass is located making them use more fuel to travel through it. Weather systems in the troposphere makes it difficult, even dangerous, for jet aircrafts to fly.