Airplanes and Contrails


When driving back home for the three-day weekend, I noticed a beautiful sunset in my rear-view mirror. The dazzling display of colors was also accompanied by crisscrossing white lines left behind by airplanes. I had always wondered what those elongated clouds in the sky were, so I decided to research more when I arrived home.

Sometimes on a cold winter day, we can see our breath in the air or see the exhaust from a car spiraling up towards the sky. The trails left behind by airplanes are very similar to those phenomenon. The white cloud lines are called “condensation trails”, or contrails for short. A jet engine emits a lot of hot water vapor into the atmosphere, which, upon contact with the extremely cold air at such a high altitude, immediately turns to ice crystals. These crystals essentially form a cirrus cloud, which expands and spreads out until it disappears.

But sometimes I see a plane in the air and no contrails accompanying it. Why is that? Simply put, the air is too dry and the water vapor dissipates into it almost immediately. The contrails last much longer in moist air because it takes time for them to be absorbed into the already saturated air molecules. Nevertheless, contrails are definitely a nice addition to a beautiful sunset in my opinion.