When a jet engine emits hot, humid air into an atmosphere that is cold and has low vapor pressure, the result is condensation. The water vapor coming out of the engine quickly condenses into water droplets and then crystallizes into ice. The ice crystals are the clouds that we see forming behind the engine. That is why the streaks we see are called contrails, short for “condensation trails.” Apparently all it takes is one person to mispronounce something and all hell breaks loose.
wy69
They were also often called vapor trails.
Interesting.
On a recent road trip, my son and I were looking at the contrails. On some days, they stretched across most of the sky. On other days, about halfway. One day, we saw only a short contrail behind one plane and none behind another. We wondered if the short or missing contrails were because of excessive dryness in the upper air.
Of course, we also shared a couple jokes about people who believe in "chemtrails."