That's odd; it's one of the easiest things I've been convinced of, especially since I've witnessed them first-hand so many times.
I could understand if you saying you're convinced of seeing airplanes with white trails behind them. But what exactly it is that follows? I'm not ruling it out, but I've not seen any hard evidence; its always speculation conjoined with pockets of evidence and an alarming conclusion. Someone is always taking a video of the white trails either from land, or from close up in another airplane and says, "See! Chem-Trails!" Um... Okay. :shrugs shoulders". Its like the type of sedevecantists who sees Benedict do something, and says, "See! He did it!? He must not be the pope!" Um... Okay. You've said nothing to convince me, and I do not see how this is affecting me either way.
And what do you suppose to do with this information, assuming your correct?
And yes, a checkerboard pattern is chemtrails, not normal flight traffic.
And yes, it's strange when some planes are leaving a chemtrail and others are NOT -- at the exact same time. I have witnessed this with my own eyes as well.
Do you know what 'normal flight traffic is? Both of my parents are both pilots; one of the first thing I remember reading was that there are different airs-paces (altitudes). How do you know the plane you're looking at isn't in military space? Or part of the international airport traffic. Texas (where you're from) has the most USAF bases in the world. Southern California has many military bases too. And if these planes are traveling in different air spaces (altitudes), you have no way of knowing. Would it be possible for planes traveling at different speed, and different altitudes to react differently with the air around them?
What are they?
It's hard to say for certain, unless we could talk to those who are behind it (and get them to admit their plans!)
So we can speculate --
Weather control? This is highly probable.
Of course we can speculate. But I would correct you in saying highly unlikely. The government is too busy making their cronies money in the war on terror ™. I don't think they're as interested in this as you are, but I've been known to be wrong before....
Also, it could be some kind of defense against a new weapon that several countries now possess.
We all know that various military projects were classified for years before the public knew about them. Who in their right mind would assume there are no top-secret projects underway right now? Planes, various spacecraft, various new weapons?
You'd have to be a naive idiot to believe that.
Did anyone suggest this? Notice you've gone from climate control to weapons in the span of a few sentences. That's my point. Who the hell knows? Until someone does, speculating / worrying does you or me no good.