What layer of atmosphere planes fly in?

Planes typically fly in the lower part of the stratosphere, which begins around 10 to 15 kilometers (6 to 9 miles) above sea level. This layer is preferred because it offers a more stable atmosphere with fewer weather disturbances and turbulence compared to the troposphere below. Commercial jets often cruise at altitudes between 30,000 and 40,000 feet, which is within the stratosphere.