The sky fills with morning contrails as seen at Cleveland Hopkins airport. Photo: Chuck Slusarczyk Jr. - OPShots.net
A question that comes up with some consistency is based on the observation that some planes in the sky leave trails that persist and spread, and other planes, in the same sky, leave short-lived trails, or no trails at all.
This difference is often used as evidence of the “chemtrail” theory, which states that the longer lasting trails (or some of them) are being deliberately manipulated for some reason. So you see helpful images like this.
These trails are called contrails. They are not smoke from the engines, they are formed when the water in jet exhaust (and there’s a lot of it, like car exhaust on a cold day) mixes with wet cold air, and condenses out as ice crystals. Contrails are actually a type of cirrus cloud. When the air is wet and cold enough the trails can stay around for a long time, and sometimes spread out.
via Why do some planes leave long trails, but others don’t? » Contrail Science.
