Airplanes are known for the white streaks left behind them in the sky, commonly referred to as contrails. These contrails are caused by a complex interplay of factors, including temperature, humidity, engine emissions and the expansion of gas as it exits the plane.
When air condenses due to high humidity levels and extremely low temperatures, clouds form. Commercial airplanes operate at altitudes where temperatures can reach -56°C, causing water vapor to condense and create the snow-like appearance of contrails.
The engines used by airplanes burn fuel and oxygen to generate thrust, which also results in combustion gases and water vapor being released. Water vapor is much warmer than surrounding air and therefore condenses to form contrails. Additionally, as gas expands from the aircraft’s exhaust, it cools down further contributing to the formation of contrails.
Contrails can be observed on a clear day but not always, as their efficiency is dependent on various factors such as altitude and weather conditions. They can even be used to predict upcoming weather changes.
During air shows or flights at supersonic speeds, aircraft may leave different types of wakes such as colored “polychrome grooves” or Prandtl-Glauert condensation clouds that take on disk or cone shapes due to sudden drops in air pressure. These wakes are not just aesthetic features but also indicate important data about flight conditions and performance.