The contrails left behind by airplanes, also known as white grooves, are a result of a complex polynomial that involves several factors. Firstly, clouds form when the temperature is extremely low and the humidity in the air reaches 100%, which occurs at around -56°C in the highest layer of the troposphere where commercial airplanes fly.
The engines used by airplanes generate thrust by burning fuel and oxygen, producing combustion gases and water vapor. The water vapor condenses due to its higher temperature compared to the ambient air and creates the snowy groove that we see on planes. Additionally, when these gases leave the plane’s engine, they expand rapidly, which further contributes to the formation of contrails.
The Anglo-Saxons refer to these wakes as “contrails,” a contraction of “condensation” and “trail.” However, not all planes leave a wake behind them. This is because an airplane’s efficiency is determined by its turbojet engine’s coefficient between work done and chemical energy produced. Interestingly enough, contrails can be used to predict weather conditions based on their nature and persistence.
During air shows, you may notice that some contrails are colored. These “polychrome grooves” are created by mixing dyes and releasing them at just the right moment, so they don’t truly represent condensation trails. Finally, there is a unique type of contrail left behind by planes that exceed the speed of sound: a disk or cone-shaped cloud called Prandtl-Glauert condensation clouds formed due to sudden drops in air pressure.