What causes clouds to form?
Clouds are possibly the most interesting (and beautiful) of all weather phenomena. While there is a wide variety of cloud shapes and sizes, they are all made of the same thing: condensed water or ice. The air in the cloud has been cooled (almost always because it is rising) and it can no longer hold all of thewater vapor it contains. Some of that (invisible) water vapor condenses to form (visible) cloud droplets or ice crystals.
It only causes clouds if the air cools to its dew point, and even then not always (although in that case you would get fog). For clouds to form, you need rising air, whereupon the air would be forced to cool to its dew point and condense if it were to continue to rise. This only happens when there is something forcing it to rise.
Misspelled it: It's contrail clouds. They're in family A, high altitude clouds. Contrails are made from either airplane exhaust or wingtip vortexes. Wingtip vortexes are essentially a drop in air pressure during flight, which causes a temperature change, which causes mositure to condense. That all leads to contrails. Airplane exhaust simply condenses to form clouds. Contrail clouds last long after the plane has left.