Contrail/Chemtrail Observation That Needs An Answer

Let me begin by stating for the record that I'm on the fence about the Contrail vs. Chemtrail issue. I'm not entirely sure what to believe.

However, for those on either side of the fence, I have some observations that need answers.

I live right in the flight path of an International Airport. From the comfort of my Hot Tub I get to observe the Take Off and Landings of jets all day long. In the process, I have noticed a few things.

1.) Yes, Contrails/Chemtrails last significantly longer than I remember as a child. I don't have statistical data to back this up, but the difference is so significant that in my mind I don't really need to it order to be convinced that this is a simple fact. If it isn't Chemtrails, then has Jetfuel really changed that drastically in 30 years even though the same jets from 30 years ago are still flying? Is it the increase of airborne pollutants? Is it a side-effect of Global Warming?

2.) Why are there never Contrails/Chemtrails at night? With rare exceptions to the rule, Contrails/Chemtrails only appear between 8am and 8pm where I live. The nights here are generally clear enough that if there were Trails they would remain visible if they were present. However, they simply aren't there.

3.) Why don't all Jets leave Contrails/Chemtrails? It's not even the type of Jet that determines whether they leave Trails or not. Two 747s can take off 10 minutes apart and one will leave a Trail and the other doesn't. The factor that seems to come into play is the Airline. Smaller Airlines don't seem to leave them while the bigger Airlines do. Why is that?

4.) I've never observed a crisscross pattern of Trails before, however I have many times seen them run parallel to one another...sometimes 5 or 6 parallel at a time. As I said, I live right beneath the Take Off Flight Paths, so it makes sense that they run parallel...and from our Airport flights either head directly North or directly South. Fair enough. However, those flights that have a flight path that takes them furtherest East or West in their flights North or South head directly over non-populated areas of the wilderness and happen not to leave Trails. The parallel Trails only appear over the populated mid-section of the North-South Corridor. Again, is this caused by Air Pollutants that linger over the populated areas? Is it from excess reflected heat from a large expanse of concrete? Or is it just something more nefarious?

Any way, these are just some of the unanswered questions I have in the back of my mind on the issue that have never been satisfactorily answered within reason. Anyone have any answers?