Yes, that would count as the most exotic of explanations. If true the program will be very difficult to halt. Also if true it implies the need a persistent presence of metallic aerosol cover - because they'd not ever want any gaps.

What I observe in practice is that the planes spray a day ahead of an advancing cold front and in the process extend the leading cloud edge beyond where it would normally terminate. Presumably creating an extended cloud shelf manipulates sunlight/heating and enhances the steer-ability of the system. After the rain has ended and the high pressure zone passes over, one to two days elapses before a new set of trails is laid down and the cycle begins afresh.

So to us little people on the ground the direct observables fit with weather engineering being the primary purpose. It also fits with the weather modification treaties between the U.S. and Canada that have been unearthed.

Tracking UFOs might be a highly secretive side benefit. Hard to say. Not all of Cassidy's interviewees come across as credible it has to be said. It's easy to make up stuff.