So what exactly is the hard evidence that these are anything other than water vapor?

Given the various theories behind chemtrails, why has no one just flown up and obtained some samples? Surely not something that would be that hard? At the very least, there must be enough people suspicious of chemtrails to commission a flight to gather samples. A pilot, plane and sampling/testing gear couldn't be THAT expensive and should be able to reasonably prove or disprove the theories.

Maybe chemtrail conspiracy theorists should start a gofundme or something to get this done. While I tend to be skeptical that these are anything other than water vapor or something as equally non-nefarious, I would contribute to such a fund to prove it one way or the other.