When you look up the sky on a clear and sunny day, you may see white smoke trails left behind by passing airplanes. Most people have seen these white smoke trails — they’ve become synonymous with airplanes. Unless you’re familiar with commercial airplanes and how they operate, though, you might be wondering how these trails are created. After all, cars and trucks don’t leave behind a white smoke trail, so why do airplanes?
Condensation in Exhaust Gases
The reason airplanes leave a white smoke trail in their wake is because their exhaust gases contain moisture that condenses at high altitudes. As the airplane’s engines release exhaust gases, moisture vapor is released as well. The cold temperature and low air pressure at high altitudes forces this moisture to condense, which creates the characteristic white smoke trail for which airplanes have become widely known.
Therefore, white smoke trails left behind by airplanes aren’t filled with toxic chemicals. Rather, they are simply the result of moisture vapor in an airplane’s exhaust gases. Airplanes typically won’t leave behind a white smoke trail when taking off or landing. For moisture vapor to condense to the point where it creates a white trail, it must be exposed to high altitudes of at least 20,000 feet.
Incomplete Combustion
Most airplanes leave behind a white smoke trail, though some may leave behind a black smoke trail. Black smoke trails aren’t caused by condensation in exhaust gases. Instead, they are caused by an incomplete combustion processes. Just like cars and trucks use combustion to produce power, so do airplanes. Fuel is fed into the engine’s combustion chamber where it’s ignited to create power. This process, known as combustion, is essential to achieving forward momentum. But some airplanes may have an incomplete combustion process in which some of the fuel isn’t completely burned.
If an engine doesn’t burn all the fuel that’s fed to it, the excess fuel will be released through the airplane’s exhaust system, which manifests as a black smoke trail behind the airplane. Black smoke trails such as this were more common during the 20th century. Advancements in aerospace engineering now allow for a more complete and efficient combustion process, reducing the risk of black smoke trails.
What About Chemtrails?
The idea that airplanes intentionally spray “chemtrails” consisting of harmful chemicals is a myth. As revealed here, airplanes leave white smoke trails because condensation is present in exhaust gases, which condenses at high altitudes, and they leave black smoke trails when an airplane doesn’t have a complete combustion process.
