Final answer:
The stratosphere extends from about 11 to 50 kilometers above the Earth's surface. It lies above the troposphere and includes the layer where most atmospheric ozone is found. Commercial airplanes often fly in the lower part of this layer.
Step-by-step explanation:
The stratosphere is the second major atmospheric layer above the troposphere, extending from about 11 to 50 kilometers above the Earth's surface. It is characterized by a slight temperature increase with altitude, contrasting with the rapid temperature decrease in the troposphere. The stratosphere is cold and generally cloud-free, and it is also where most atmospheric ozone is concentrated. The boundary between the troposphere and the stratosphere is known as the tropopause, which can vary in height but is generally found at 11-13 kilometers altitude in the mid-latitudes. Most commercial airplanes fly in the lower part of the stratosphere to avoid the turbulence which is more common in the troposphere.