I first began noticing regular, patterned, chemtrail spraying in my area around January 1, 2008.
There is a website,
http://flightaware.com, that you can use to view live radar tracking of passenger jet aircraft in your local airspace.
What I find in my area is that on most occasions, the flights laying down the chemtrails do NOT correspond to commercial passenger jet aircraft in the local airspace.
My conclusions: chemtrails are real and are being laid down by non-passenger jet aircraft.