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Learning moment - Why do planes have white tails?

In Indio this past week I’d walk and see streams of white following the planes, actually so many of them that it made the photos absolutely stunning. What are these white streams? I’ve thought about it so many times and when Sarah and I were sitting at the pool we both were curious. So, in this world of technology, I Googled it and here is what I found….



Contrails, short for “Condensation Trails” or also known as vapor trails are line-shaped clouds produced by aircrafts. Jets leave white trails for the same reason we can sometimes see our breath. The hot, humid exhaust from jet engines mixes with the atmosphere and the water vapor contained in the jet exhaust condenses and freezes in the right ambient temperature. This mixing process forms a cloud very similar to the one our hot breath makes on a cold day.


Engine exhaust is primarily made up of water and carbon dioxide, the combustion products of hydrocarbon fuel as well as many other chemical by-products. At high altitudes the water vapor that emerges condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails. These contrails usually form at above 8,000 meters (26,000 feet), where the air temperature is -36.5°C (-34°F). They could also form closer to the ground if the air is cold and moist. Really a simple process….


Another effect jet engines have in our skies are distrails, short for dissipation trail. This is when an aircraft passes through a cloud and it disperses the cloud in its path. This happens because the plane’s warm engine exhaust and enhanced vertical mixing in the aircraft’s wake causes existing cloud droplets to evaporate. If a cloud is significantly thin, such processes can yield a cloud-free corridor but if it is a solid cloud, we can see the path cut into the cloud.



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