The stratosphere is the layer of the Earth’s atmosphere where most aircraft reach their cruising altitude. It’s the second major layer, and it is located below the mesosphere and just above the troposphere. The stratosphere contains roughly 20 percent of the atmosphere’s mass.
Because bacterial life can survive in the stratosphere, this layer of the atmosphere belongs to the biosphere. Some species of birds have even been reported to fly in the lower levels of the stratosphere. In a bizarre accident, reports exist that a vulture was actually sucked into a jet engine at 30,000 feet.
The Temperature of the Stratosphere
In the stratosphere, the temperature is stratified. Cooler layers are closer to Earth while warmer layers exist above the cooler ones. The border between the stratosphere and the troposphere is where temperature inversion is most prevalent. However, the temperature in the stratosphere can vary depending on the seasons.
Aircraft in the Stratosphere
Commercial airliners generally reach their cruising altitude in the lower levels of the stratosphere at an altitude between 30,000 and 39,000 feet. This altitude optimizes fuel efficiency since the temperatures are lower here.
Because the temperature between the lower layers of the stratosphere and the troposphere are somewhat consistent, very little turbulence exists here.