Contrails: Cool Clouds or Crazy Conspiracy?

Contributor: Lindsey Congalosi. Lesson ID: 13179

It's a bird! It's a plane! It's a contrail! It's a government conspiracy? What? Those thin clouds airplanes leave behind them while flying are completely safe and explained by science! (Yay, science!)


Earth Science, Physics

learning style
Auditory, Visual
personality style
Beaver, Golden Retriever
Grade Level
High School (9-12)
Lesson Type
Quick Query

Lesson Plan - Get It!

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many white lines in sky

  • Have you ever seen those long white clouds formed by airplanes flying through the sky?

These clouds are called contrails, and they are completely natural and safe.

When an airplane flies through the sky, it often leaves a trail of white.

  • What is that trail made of and why does it occur?

thin contrail far away

The white line following an airplane is called a contrail. Contrail is short for condensation trail.

They are formed by the normal actions of an airplane.

For a quick overview of aerodynamics to get ready for the rest of our lesson, watch How do Airplanes fly? from Lesics:

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As you just learned, airplanes run on jet fuel. Jet fuel is different than car fuel.

For an explaination, watch What's The Difference Between Jet Fuel and Car Fuel? from Seeker:

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When burning jet fuel meets air, a chemical reaction occurs. The chemical bonds in the jet fuel are broken, producing energy that propels the plane forward, allowing it to fly.

When this chemical reaction occurs, hydrogen and oxygen combine to form water as a natural byproduct. The water is then released into the air.

  • Why is the contrail visible if water vapor is invisible?

plane contrail over water

When a plane is flying at its top altitude, it is approximately 35,000 feet above the ground. Temperature drops as we get higher up in the troposphere, the lowest layer of the atmosphere.

(If you want to learn more the atmosphere, check out our lesson found under Additional Resources in the right-hand sidebar.)

plane with four contrails

At 35,000 feet, the temperature is approximately -50ºC, much colder than the freezing point. This drop in temperature causes the liquid water to condense and freeze.

The condensed water or ice droplets are just as easily visible as a cloud. In fact, this is how clouds are formed.

(More on clouds can be found under Additional Resources as well.)

Okay, one more video. Watch Crash Course: How Contrails Form from Boldmethod:

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Now that you've learned the facts about contrails, head over to the Got It? section to learn about some of the common misconceptions regarding contrails.

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