I'm going to squash this idiotcy right now.
1. Air is a fluid just like water. There are currents, hot and cold spots, eddy's etc. You could run through several layers horizontally and vertically, with just enough difference in temp/dew spread to cause contrails to appear and disappear from the same jet at the same alititude. You can have the exact same aircraft, changing a few thousand feet in altitude, leave very different contrails. Individual engines or different power settings cause cause differences in the amount of water vapor. Hell, you don't need engines to leave contrails at all...I can tell you of a time in a B-1B where I left huge contrails off the coast of Florida during William Tell. It was coming off the wings of our formation in huge sheets that looked thick enough to walk on. Or the time I left a couple of huge circular contrails in a T-38 while doing a supersonic high G run at 40k to 30k...looked back to see what looked like a giant 3d 'S'...because of the G I was pulling. All related to the same effect that causes those pretty transonic cones folks see.
2. Aircraft fuel dump in distress. Or they dump water for tests (such as icing tests), or they burn oil in the exhaust for airshows, or for evaluating airflows...there are about a billion ways an aircraft could have a trail behind it. Did you know a lot of larger aircraft have an APU in the tail? So if you fire it up, you leave an exhaust which has...guess what...water vapor which can be a different content ratio than a regular aircraft engine (actually, APUs are fairly inefficent anyway)...so, yes Virginia, you can con from an APU yet not from the engines ON THE SAME AIRCRAFT.
3. Now, lets talk about distances, shall we? I hear this every once in a while that somehow someone knows that aircraft are at the same altitude because they are very close in size. Not necessarily. Here's a nice math exercise you can do to figure out why seeing is not believing. It's the same exercise I use to explain to new pilots why the WORST way to rejoin on another aircraft is to head directly at it.
A) Break out your geometry and trig skills, you're going to need them. First, pick an object of a fixed size...or use an arbitrary length (lets say 200 feet).
B) Set that object at a fixed distance from your eye (lets start at 30000 feet).
C) Assuming the end points of your object are perpendicular to your eye, note that it forms a nice triangle that can be divided lengthwise to form 2 identical right triangles.
D) We can now figure out the angle of arc the object takes up in our field of vision using the inverse tangent function (for our example, about 22.9 minutes of arc). Here, I'll even provide the formula:
X = (minutes per degree of arc) x (2) x (inverse tan ((length of object / 2)/distance of object) = 60 x 2 x atan((Y/2)/Z). If you draw it out, you'll see exactly what I'm showing here.
E) Now, start adjusting the distance parameter and recalculate. Take all your results and chart them on a graph. Note the interesting thing...the graph is not a linear curve. In fact, it stays pretty flat until near the end. Which means that when objects are far away, estimating relative distance becomes more and more difficult.
F) The accepted number is that an average human can note change with approximately 2 minutes of viewing arc change. This assumes a clear, high contrast situation with a non-moving target (ie the target is not sweeping across your field of view) at maximum eye resolution. You start throwing other varibles (multiple targets, sideways vectors, contrast/brightness changes) and the threshold to note a change only goes up. Heck, looking at our math...you can't even tell the distance change until the target has changed altitude by at least 2000 feet. And did I happen to mention this becomes progressively more difficult the smaller the target is?
4. I hear a lot about a global chemtrail conspiracy. Yet, not one reliable person has ever come forward anywhere and said, "Yes, I was a part of it." In the history of real conspiracies, in almost every case, it only took one person to bring the whole thing crashing down. And this was before the age of the 24/7 information access and ubiqitous cameras. And yet, out of the literally hundreds of thousands of people that would be needed to actually do such a thing, not one reliable person has ever been found? In this day of governments with more leaks than a colander?
5. Oh, and as a commerical and military pilot myself, I have to ask...exactly what would be my motivation to have this crap sprayed on my head? My families' head? Somehow, every single person involved would have to be coerced into doing such a thing and NOT ONE PERSON would say "Enough is enough?". Men who have been through hell and back and not one would say "I risk falling on my sword because it is the right thing?" Please.
So, put away your tinfoil hats, the black helocopter you hear is actually your neighbors' lawn mower, and I'm pretty sure the only mind control is from the 'Entertainment' part of your TV.
FC