During winter, sometimes we see a white trail at the back of a flying aeroplane in a clear sky. Explain why.

Explanation

In winter, air temperature is low, Hence, when an aeroplane flies, the vapous released humidity of the air surrounding the plane is high, we see this white trail at the back of the plane for a long time before it disappears. If the relative humidity is low, the white trail is short and disappears quickly. if the relative humidity is very low, there is no formation of the white trail.