That doesn't sound unusual at all. Wouldn't the mid-1990s correspond to roughly the time that high-bypass turbofan engines became widespread on commercial jets? Shouldn't be at all surprising that a different kind of jet engine produces a different kind of contrail.
That’s just it. If you re-read my post, I mention that, from my deck, I can watch plenty of commercial jets. These are easy to identify by their markings with binoculars. I’ve observed they have normal contrails, that is, contrails that dissipate.
However, sometimes, there other large white jets flying at the same time as the commercial jets but at a higher altitude. They are plain white, unmarked, and criss cross the sky. That is, they fly back and forth across the sky until their persistent contrails are streaked all over the visible sky like a kid fingerpainting on a paper. They don’t travel in just one direction as with a commercial plane going to a destination. There are no markings visible on these whiyte jets. None visible through the binocs. These leave contrails that do not dissipate but persist and spread out to form something like large bands of clouds that will block the sun on a day that was only a hour or two before a clear blur sky day. If you can explain what these unmarked white jets are doing, I might believe the EPA feds who came out on March 13 and said we at EPA are not aware of aerial spraying of chemical aerosols from jet aircraft. I put about as much trust in the EPA as i do in Obama. Funny they didn’t deny there is any spraying going on. Some time ago, I read an article in Popular Science on geo-engineering of climate that said aerosol spraying of barium and some other chemicals was proposed for reducing global warming.