[Carl in Tampa]

Contrails have existed since airplanes have been capable of flying high enough to produce them. They are created by the heat and moisture from the combustion in aircraft engines coming in contact with very cold air. The duration of their persistence is related to the weather conditions at the altitude at which the aircraft is flying at any particular time.

I assure you that the Germans saw a lot of them during WW II. (See below.)

The theory that there is a conspiracy to introduce harmful chemicals into the contrails to produce "chemtrails" can be avoided by wearing a tinfoil hat at all times.