Chemtrail guy;
Airliner jet engines burn a lot of fuel.
https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft
A range of anywhere from 8 to 25 pounds of fuel per mile seems to be common. If we use a common flight speed of 450 miles per hour, we are looking at traveling 7.5 miles per minute, giving a range of 60 to 187 pounds of fuel PER MINUTE. It's possible that my math here fucking sucks because it was done hastily, but the specific numbers aren't that important–the important thing is that quite a few gallons of fuel are burning up in the engines and shooting out the exhaust continually as the plane passes through, at high altitude where it is cold.
All of the mass of the fuel (usually kerosene) is conserved when it is burned with oxygen to create water and other byproducts, giving a vapor trail with a mass greater than the burned fuel originally had and a volume many many times greater than it originally had. In order for the vapor trail to dissipate, it must achieve a combination of warming up and spreading out until it reaches atmosphere with room for more water to dissolve into it. Until this occurs, it exists as a cloud of water vapor, and how long it takes to dissipate depends on a lot of factors; relative humidity, air pressure\density, wind activity, fuel variations, flight speed, and more.
I'm not saying chemtrails don't exist–I have no evidence that proves it one way or the other–but seeing lingering vapor trails after a plane passes by is absolutely no guarantee that you are being gassed by ze Jews.