Well, the trails are not always contrails. They are geoengineeing to dim the sun.
This is going on for some years "experimentally" and was recently approved by government.
https://www.forbes.com/sites/arielcohen/2021/01/11/bill-gates-backed-climate-solution-gains-traction-but-concerns-linger/
https://www.sciencealert.com/harvard-scientists-say-reflecting-the-sun-
This is going on for some years "experimentally" and was recently approved by government.
the Guardian
UK scientists to launch outdoor geoengineering experiments
Blocking sunlight could temporarily slow the climate crisis but the technologies remain highly controversial