I remember back in the early 1980's the USSR's Kremlin openly spoke about how they were open to "Seeding the Clouds" to make sure they had good weather for their huge Moscow Parade....
They bragged how the USSR had been able to manipulate the rain for years...
Who knows...
My Son is an Air Force Staff Sargent and knows every single part of most planes in the Air Force. When I asked him about a chem trail apparatus to spray, he said he had never seen anything like that mounted on any US Airplane ever. It's his job to know these things because he signs off on all maintenance on all planes in his base and is responsible for anything that fails during any flight....
Now he does not have any knowledge on Commercial Aircraft and if that is the way chem-trails are being sprayed, my guess is it is only Commercial Flights...