Why do Commercial airplanes have smoke that comes out of the back while flying sometimes?
It’s not smoke, it’s water. Jet engines (all engines, in fact) produce primarily carbon dioxide and water in their exhaust. The carbon dioxide is an invisible gas and stays that way after leaving the engine. The water is also an invisible gas when it first comes out of the engine, but if the air around the airplane is cold enough, the water condenses into a liquid or even into ice crystals, and these produce a white fog that looks like “smoke”. But it’s not smoke, it’s water, and it has exactly the same composition as other clouds that you see in the sky. This white trail of fog is called a condensation trail, or contrail for short. It forms whenever the conditions of the atmosphere around the airplane are right. In average atmospheric conditions, it’s cold enough for contrails to form above around 26,000 feet, but sometimes they form at lower altitudes, and sometimes they don’t form at all. The contrails may disappear shortly after they form, as the water evaporates again, or they may
