What chemical is released by the aircraft that leaves a lengthy white cloud stripe way up in the sky?

sometimes when I look in the sky, I see some type of aircraft leaving an extremely lengthy trail of white cloud like dust or something of the sort.

wondering what the chemical is, what type of aircraft, and what the purpose is.

sources helpful.

thanksWhat chemical is released by the aircraft that leaves a lengthy white cloud stripe way up in the sky?
These are known as "contrails" and the bits that you can see are ice crystals formed from the water vapour exhausted from the aircraft engines. The engines also exhaust CO2, but you can't see that.



The aircraft normally has to be quite high for the air temperature to be cold enough to allow these to form and therefore it is unusual to see them formed by anything other than jet aircraft.



**EDIT**

Sorry - forgot to give you a link.What chemical is released by the aircraft that leaves a lengthy white cloud stripe way up in the sky?
its the exhaust, it just looks different because its at a higher altitude.What chemical is released by the aircraft that leaves a lengthy white cloud stripe way up in the sky?
its nothing but the exhaust vapors if the military could ever figure out how to stop the trails then jets would be per say invisible