Have we considered that this is all due to a fuel additive. If I was going to spray the whole world I would add nano shit to the fuel at the refinery. Then all planes are my transport system and I don't need flight clearance. There are plane routes world wide.
Of course that doesn't explain the phots of dedicated spray vehicles. But maybe those are weather mod experiment planes leaked to throw us off? Just a theory I have been brewing for a while.