This is a bit hard to explain <lol> but

When you look out the window there is often lines and smokey stuff of airplane lines, and it stays for quite a while....

It looks like a lot, I was just wondering is it a lot, and I mean how bad is it for the world? :(

Is it airplane fuel stuff. I always thought it had something to do with the plane shifting the air from one place to another. Like a boat making waves. Whahahaaa, you don't want to know what goes on inside my head.

I thought it has something to do with condensation (water in gasform that turns into liquid state very quickly). Of course, airplanes do leave gasclouds, like cars do, but the stripes you see in the sky aren't smogclouds that cars leave behind when they pull up very quickly.

I'm not entirely sure if those airplaneclouds have to do with condensation, but the thing is that you only see them when it's a clear sky.
In fact, for me, those planeclouds tell me in the morning if the weather that day is gonna be good (Rolly)

I think Jo's correct. Just looked it up on a Dutch website.

I know its late, but I only just found this thread again. Thanks you two. I glad its not waste rubbish otherwise I dread to think about the polution that comes out of it. :(

I agree about the good weather. No clouds and lines from planes = a hot hot day.