Simple answer on contrails: over the last several decades, jet engines have changed to offer higher bypass ratios. The amount of air pushed around the jet engine by the turbofan as compared to the amount directly pushed through the jet has increased. This means more moisture is compressed to higher pressure and exposed to hot jet exhaust before rapidly expanding, cooling, and condensing.
I don't think it's a coincidence that these ratios jumped to around 8:1 in the 90s when chemtrail theories started to spread. Now 10:1 and even 12:1 are common in jet liners as they pursue greater fuel efficiency and power. Most passenger jetliners only have 2 massive engines now, too.
Additionally, the pictures I have seen purporting to be chemical spray tanks and what it this far have all had much more mundane explanations that make more sense.
It's not that I don't think government would spray us with unknown agents, because the evidence of history and public statements about current events suggest they can and do often treat us like guinea pigs. But so far the chemtrail claims have not passed the threshold of persuading me with evidence, and what I do know of physics tends to pass Occam's Razor.
I've read that argument but it doesn't explain what's happening. Our place is very rural and we're far away from any flightpath. Besides, these are very small planes that fly backwards and forwards, going nowhere and leaving behind vapour that does not dissipate but expands.
The one argument I can't get past to fully embrace the chemtrail thing is that if they are spraying us, they are also breathing the air.
You can always check flightaware and other sites which track transponders for commercial aviation to see what's up there, where they are going, and how high it is.