As we all are aware that jet leaves a white trail when flying high in the sky but it doesn’t when it takes off or when it’s too low. The story changes in the high sky due to very cold temperature up there.
The white trails which the planes leave behind are actually artificial which are known as contrails, shortened version of ‘condensation trail’. Exhaust created by the jet engine contains carbon dioxide, unburned fuel, oxides of nitrogen and sulfur, soot, metal particles and water vapor. As the water vapor in the exhaust strikes the extremely cold air with temperature of -40° F at the height of 26,000 ft or more, they instantly freeze into the ice crystals. It often disappears in seconds as crystals gasify back in to the vapor.
The thickness, extent and duration of the contrail depend on the plane’s altitude, temperature and humidity in the atmosphere. The lastingness and nature of the jet’s contrails can be helpful in predicting the weather. A thin and short contrail indicates a fair weather and a low-humidity whereas a thick and long-lasted contrail indicates high humidity and an early sign of storm.
Some airplanes create messages in the air show with what looks like cloud. Don’t confuse them with contrails. They are the skywriters who use small airplanes featured with special smoke machines to create messages by flying in special patterns. Those smoke machines are usually comprised of pressurized containers of oil which opens up to spray the oil in the pilot’s hot exhaust system on the pilot’s command, where it burns and create white dense clouds of smoke.
Article by Nishant.