of course they exist everyone an see them  and yes they can seed clouds  question is how does the chemtrails affect you and or life on the ground in general  in comparrison to the exhaust gasses of personal combustion vehicles not so much after takeoff the temperatures inside of the aircraft engine are usually hot enough so that not much pollution remains when they are on the ground just before takeoff and after landing when they have shut down their engines on the parking spot that is when aircraft engines heavily pollute the air in their environment  so if you aer living on an airport apron you should consider moving for your own health
Germany