Contrails And Why Do Some Airplanes Leave Them Behind

Well, you must have noticed that as some airplane fly through the sky, sometimes a trail of what seems to be smoke is left behind. However, these trails are mostly condensation and hence are called “contrails”, short for “condensation trails”.  A great deal of water and some aerosols are ejected into the air as the engine burns. When water vapor condenses and freezes around small particles generated from the engine exhaust, ‘contrails’ are formed. Water and the particles both are responsible for the creation of contrails.

Despite the fact that some elements in the gas do not participate in the generation of contrail, they are still considered pollutants. In general, an aircraft’s emissions consist of carbon dioxide, water vapor, nitrogen oxides (NOx), carbon monoxide, hydrocarbons such as methane, sulfates (SOx), and soot and metal particles.

Contrails And Why Do Some Airplanes Leave Them Behind

A large amount of water, about 2.75 kg of water per second, is ejected by airplanes such as the Boeing 747.


Although contrails vary significantly in their life span, they are exceptionally similar in composition. The weather has a direct effect on the lifespan of the contrail. Generally, contrails have been categorized into the following three distinctions:

1. Short-lived Contrails

They are the short white lines which tail the aircraft and last for only a few minutes. These trails vanish almost as soon as they are created. This is because of the fact that the air through which the plane travels is slightly moist with only a small amount of water vapor available. So, any ice particles that are produced return back to a vapor state rapidly.

Contrails And Why Do Some Airplanes Leave Them Behind

2. Persistent (Non-Spreading) Contrails

These contrails are much longer white lines that remain detectable for a long time even after the plane disappears. The reason is that the air which the plane travels through is somewhat humid with a large amount of water vapor available to generate a trail.

Contrails And Why Do Some Airplanes Leave Them Behind

3. Persistent (Spreading) Contrails

They are just like non-spreading trails except for the fact that they spread out over a larger distance due to turbulence or other weather conditions. Their large area and life longevity make them the most likely to affect climate.

Contrails And Why Do Some Airplanes Leave Them Behind

The contrail cousins bear a resemblance to contrails; however, they vary a little in the physical process which generates them. Vapor trails are one of the most common types of contrail cousins which spread from the wingtips of a jet, normally during takeoff or landing. Weather permitting, if the pressure of the vortex at the end of the wingtip drops enough, a trail will create. Liquid water creates drops inside the vortex under the right conditions, thereby making them visible. Nevertheless, they quickly evaporate after they are formed.

Well, the real question is ‘are they dangerous?’ The answer is that the usual contrails observed behind aircrafts are not dangerous as their key component is pure water. Jet fuel is also highly refined to eliminate as many contaminants as possible. Inside the engine, a large amount of gas must quickly flow through to the combustion chamber to keep the turbine spinning. The travel time of the fuel through small tubes inside the engine is liters per second. The slightest imperfections can result into a buildup which can turn out to be lethal.

Contrails And Why Do Some Airplanes Leave Them Behind

An engine overhaul is very expensive, reaching into the millions of dollars. Special precaution is taken regarding the fuel being used in the planes which must be of the highest quality. At each refuel, the time, location, and amount of fuel are recorded to link back to the source in the event of an unlikely accident.


Chemtrails turned into a famous figure after a 52-page report was given to the Airforce in which the probability of modifying weather patterns and using it as a force multiplier was examined. The operational capabilities divide into two directives, degradation of enemy forces, and enhancing friendly ones. The weather could be altered to degrade enemies or increase friendly forces. The plan included increasing storms and floods to not only destroy communication lines, but also to cause mass droughts. Friendly forces were to be cloaked behind fog while improving upper atmosphere weather to receive greater satellite connection.

Contrails And Why Do Some Airplanes Leave Them Behind

So, did it work? Well, not really. Several countries have tried to take the entire weather system into their own hands which is still a mystery. However, scientists have succeeded in modifying one aspect which is precipitation. The first man-made rainfall was produced in the 1940’s by Irving Langmuir and his assistant, Vincent Joseph Schaefer.

On November 13, 1946, during the research on wing icing, Schaefer poured out a bag of dry ice weighing a few kilograms from an airplane into a supercooled cloud. He then flew his plane under the cloud and witnessed snow falling from the sky. This snow turned into rain by the time it reached Langmuir on the ground. This phenomenon was called ‘cloud seeding’. It is the process of artificially modifying the weather to produce precipitation. As the dry ice falls through the cloud, water vapor which trails it condenses into rain. The rain continues to grow until the cloud from which they are suspended cannot contain them, causing them to fall.

Contrails And Why Do Some Airplanes Leave Them Behind

One of the other schemes is spray of particles into the air in order to capture the moisture and cause it to accumulate. Dust, smoke, or sea salt particles are injected into the area to stimulate precipitation. Silver iodide can also be used to influence vapor to fall out of gaseous form.

Both of these methods are in use for influencing some weather patterns. However, the process can only be implemented in areas of extreme drought and pollution.

Now, the next question is ‘are chemtrails harmful?’ Again, most of the chemtrails in the sky are contrails and hence majority of the trial is just water vapor, therefore, it does not cause any harm. But, some contrails absorb a lot of thermal energy from the sun, potentially contributing to global warming.

Contrails And Why Do Some Airplanes Leave Them Behind

Nonetheless, aircrafts are engineered to be as fuel efficient than ever. These days, some airliners are even more efficient than new car models. While there are some regions which need cloud seeding, most of the world stays unaffected by the contents which are ejected from the engines. In hindsight, airliners do not spread chemicals into the air. Weather modification aircraft are a division of their own to modify very specific areas around the earth. Apart from the very few airliners which are utilized to assist farm crops, the majority of aircrafts do not have any influence on the weather. This implies that it is not just airplanes that are polluting the skies.

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