Chemtrails: What Are They and How Do They Form?

At some point or another, we’ve all seen those cloud-like trails in the sky left by planes and other aircraft and wondered what they are and why they form. 

Some of you may have heard the term “chemtrails” used when talking about these cloud trails, which basically refers to the conspiracy theory that these trails of condensation are actually chemicals released by the government. And while this may seem like a legitimate theory given the fact that some of the trails disappear faster than others, nothing could be further from the truth.

So if they aren’t chemtrials or simply just smoke, then what are they?

The word contrail is actually short for condensation, which means that those trails form when the water in the jet exhaust mixes with the cold, wet air in the sky and then condenses into ice crystals to form a type of cirrus cloud; or what we see from the ground as contrails. So when the air around the engine is cold and wet enough, the water in the exhaust will mix with that air to leave contrails that linger in the air for a period of time after the aircraft passes. In other words, the colder the air is surrounding the engine, the more likely that cirrus cloud, or contrails will form, persist, and spread throughout the sky.

But why do some planes leave contrails and others don’t?

For those who endorse the chemtrail conspiracy theory, they will often cite the fact that some planes leave trails and others don’t, as evidence that these are chemicals released into the air by the government. The problem with this theory is that, in addition to the fact that the condensation is just that and not chemicals, is that the appearance of the contrails will look different from our perspective based upon both he type of the plane leaving the trail, as well as the altitude of the plane at hand. Different planes made with different engines will naturally have different reactions to the cold, wet air at different altitudes, so when we see a contrail left by one aircraft that lingers and spreads out over the sky, a completely different aircraft might not leave a contrail at all.

Why do some planes appear to leave contrails at altitudes that other planes don’t?

Similar to the reasons stated above, the cold and wet air reacts differently with the exhaust from jet engines depending upon the altitude at which the plane is flying. So while a plane flying at an altitude of 32,000 feet might not look like’s actually flying 3,000 feet below another plane leaving a contrail at 35,000 feet, the air surrounding the plane at the lower altitude could be warm, dry air, which is why that plane doesn’t leave a contrail and the plane further up in the sky, does. Remember that the temperature and density of the air surrounding the engine of the aircraft has just as much of an influence over the appearance of the contrails as the altitude of the plane, and the type of engine itself.