The external temperature of these planes decreases and then increases as they leave the stratosphere and return to the ground.
This occurs as the airplane initially goes up via the troposphere while traveling through this layer, the temperature of the plane decreases as they go higher. However, when the plane goes into the frontier between the troposphere and the stratosphere, that is, the tropopause, the temperature elevates.
This increase in temperature is a result of the ozone layer that is present in the stratosphere and absorbs the UV rays from the Sun, making an elevation in temperature.
