Have you every noticed, especially on a clear, sunny day, that planes leave a trail of what looks like white smoke in their wake? Ever wonder why? I did. Here’s why it happens…
It turns out it’s all due to condensation. A plane’s exhaust gases have moisture in them, and when the plane is at higher altitudes (think 20,000 feet and higher), the colder temperature and along with the low air pressure forces the moisture to condense. The condensed moisture vapor freezes if it’s cold enough, and when it does, this makes something that looks like thin, white clouds that trail the plane’s engines.
The trails are commonly known as contrails (short for condensation trails) or vapor trails. It’s sort of like what happens when you can see your breath on a really cold day – the moisture in your breath meets the cold air and freezes.
Sometimes the vapor trails are thin and sometimes they’re fluffy. Sometimes they’re inconsistent and eventually start or stop. All of that is due to the plane’s altitude, as well as the outdoor temperature and humidity of where it is at the time. So if you see two planes at the same time but they have two totally different shapes of trails, or if one has a trail and one doesn’t, it’s because they’re at different altitudes, and therefore different air temperatures and air pressures.
Fun Fact! What the trails look like can help predict the weather. For example:
- Fair weather = a thin, short-lived contrail (it usually means there’s low humidity in the air at that higher altitude)
- Storm is coming = a thick, long-lasting contrail (more humid air at higher altitudes)
There’s a conspiracy theory that the trails are made of chemical or biological agents that are being sprayed onto the public for evil purposes (they call it “chemtrails”), but….yeah, no. Contrails do contain pollutants from the planes’ exhaust, but not chemicals that are purposely being sprayed on us for who knows what nefarious reasons.
Speaking of chemicals…contrails are not the same as what skywriters use. Skywriters use smaller airplanes that have special smoke machines to make their written messages you can see from the ground. The smoke machines usually use pressurized containers that have oil in them. At a pilot’s command, the machines spray the oil onto the plane’s exhaust system. The exhaust system is hot so the oil burns quickly and creates clouds of dense white smoke.
Feature Photo: Max Pixel
Like this post? Please share it! We have plenty more just like it and would love it if you decided to hang around and get emailed notifications of when we post. Or maybe you’d like to join our Facebook group – we have 14,000+ members and we talk and ask questions about travel (including Disney parks), creative ways to earn frequent flyer miles and hotel points, how to save money on or for your trips, get access to travel articles you may not see otherwise, etc. Whether you’ve read our posts before or this is the first time you’re stopping by, we’re really glad you’re here and hope you come back to visit again!
This post first appeared on Your Mileage May Vary
