Here's why:
* Density: The troposphere contains most of the Earth's atmosphere, making it the densest layer. This density provides sufficient air for the plane's wings to generate lift.
* Weather: The troposphere is where most of the Earth's weather occurs, including clouds, rain, and storms. However, planes generally fly above the majority of this weather.
* Temperature: Temperatures decrease with altitude in the troposphere, which is ideal for aircraft performance.
While some planes, like high-altitude research aircraft, may venture into the stratosphere (the layer above the troposphere), the vast majority of commercial and private planes operate within the troposphere.
