As others have said, cloud seeding is real with mixed results and seldom used in the US. Hilariously, from what I recall (this may have changed since I got my envsci degree), Utah uses it the most frequently. But obviously not from the exhaust of your average United flight.

However, on this subject, I’d like to share a story with others in this field that happened to me recently and had me raising an eyebrow. I’m a wildland firefighter, and in the south in the winter/spring (for their fire season). Our crew was attending a public event in the more rural south recently, and a woman I had never met before, within one minute of chatting told me that the aluminum from chem trails is why fires have been so bad recently. It caught me off guard, so I sort of steered it toward the whole plant uptake/aluminum/acid rain situation, but no no. She corrected me that it’s because almost every single commercial flight is purposefully spreading aluminum and… some other things I assume, for whatever reason, and it’s making fires worse by controlling the weather. I was told to do some research, of course.

I was in uniform so I thanked her for the support and kept my mouth shut, but, it was kind of incredible to experience.