I've video taped planes leaving contrails in patterns. It seems pilots don't like to fly through a contrail, so they keep laying a new one parallel to the earlier ones. When you have cross traffic, it creates a grid pattern. If they last a long time, you end up with an overcast sky.
It looks freaky. Like they are doing it on purpose. You can see satellite images of extreme overcast in heavy traffic patterns. I know it is just paraffin oil, naphtha-kerosene, alkylated phenols, some dinonylnaphthylsulfonic acid, corrosion inhibitors, icing Inhibitors, Biocides, and water vapor, but still, all that crap floating down in the air is strangely disturbing.
Unless you don't give a crap what is in the air you breathe ...