this is not touchy-feely stuff, this is hard science.
you have to know some things... for instance...
(1) how much air goes through a big jet engine every second?
(2) how much fuel goes through a big jet engine every second?
(3) how much water is produced when that fuel is burned?
(4) taking the answer from question (1), above, how many cubic meters does that air occupy at 35,000 feet?
(5) the water produced by combustion is evenly distributed though the volume of air that's expelled as exhaust from the engine... that's the volume you arrived at from the answerr to question (4)... would that volume be visible from the ground if the atmospheric conditions caused the water to condense?
if you guys are not serious enough to do your homework, you're not to be taken seriously about chemtrails.