I've been watching a Syfy Channel film called Ice Twisters, in which their drones, while trying to create rainclouds, accidentally bring down weather from the colder levels of the atmosphere that create ice-tornadoes.
Lately, I've noticed that there seem to be a lot of chemtrails in the sky just before rain and the huge snowstorms of this last winter. Is this just coincidence, or has someone been seeding the clouds, to produce precipitation?
You must remember most science fiction and disaster/horror movies bend scientific principles well past the breaking point. The only limit is how far the budget will go creating computer generated special effects.
With Internet based sites offering price comparisons for ticket prices airlines are usually quite competitive about their prices. That is why there are the occasional bankruptcies and mergers. The don't have enough revenue to be incurring the expense of dispersal equipment, supplies and maintenance for endeavors other than their primary businesses of moving passengers and a limited amount of air freight.
The "trails" are condensed water vapor already present in the air plus exhaust from the fuel/air combustion that powers the fan jets. Hydrocarbon fuel plus atmospheric oxygen in combustion produce carbon dioxide and steam (also applies to ground vehicles, ships and fossil fuel power plants). Under some circumstances atmospheric nitrogen and fuel contaminants like sulfur add small quantities of other compounds to the exhaust. Water vapor has problems forming droplets/sleet/snowflakes without an existing core to form around and air can become quite saturated. A passing plane can be all that's necessary to initiate a sudden condensation process.