What is that cloud-like image I see on planes, mostly high performance, behind their wings as they maneuver?
What causes this? It seems to disappear just as fast as it appears.
What you see behind the plane’s wings (but in fact, behind the engines) is known as condensation trails or contrails. Sometimes, they are very clear and well defined; other times they are just thin lines seen across the sky. Some days they are not so clear and on other days, do not exist at all.
Contrail forms because of the presence of water vapor from the jet engines. This is one of the components from its exhaust. Jet fuel is made of carbon and hydrogen. When jet fuel burns with oxygen, most of the exhaust that comes out of the rear consists of carbon dioxide and water. The water generally exits as an invisible vapor.
I am sure you would have noticed that when you exhale or open your mouth to speak in winter, cloud of condensation would form due to the invisible water vapor from your breath.
In the summer, you don't see your breath but in the winter, when the moisture in your breath mixes with the cold air, the moisture condenses into a visible cloud.
This same thing occurs from a jet engine in the upper atmosphere. If the temperature and humidity are right, contrails would form when the moisture in the exhaust condenses.
That is why, you often see a lot of contrails crisscrossing on a clear day that generally mark the routes of some major airways but would soon become distorted when blown by strong winds and gradually dissipated from the sky.
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