Runetrails
It will probably shock people to hear that the entire ‘chemtrails’ thing has a fragment of a flicker of a technicality of a smidgen of a basis in reality. Sort of. Well, not really, but there is a tiny grit of truth out there that was later turned into a nacreous sphere of conspiracy theory. And this was encouraged, too, on the sensible grounds that there’s nothing like a conspiracy theory to hide an almost, but not quite, unrelated actual conspiracy.
It goes like this: magic? Totally real. It’s totally really slow, totally really weak, and totally really imprecise. Which is why we — to reference one of Niven’s Laws — never used it as the basis of human civilization; there was a limit to how many people we could afford to have go live in a tower and spend fifty years learning how to reliably cast a couple of spells. But, ironically, the rise of our current scientific-industrial society has ameliorated things a bit. Thanks to modern electronics and cybernetics, we can get around the ‘imprecise’ and ‘slow’ problems; but ‘weak’ remains. What’s the point of being able to cast spells if the runes you’re inscribing to cast them have to be literally the size of a county in order to have enough juice to be worth it?
And that’s when somebody remembered that humanity has mastered powered flight. Airplanes were already drawing lines in the sky that were hundreds of miles long; all that needed to be done was to make that line-drawing symbolically deliberate. And that’s just a matter of picking and choosing which lines to incorporate into the runes being ’drawn.’ Which is completely beyond the ability of a human to do quickly enough, of course, but it’s not beyond the ability of a computer with the right software. Particularly when the reputable governments of the world have made a tacit agreement to make sure that certain useful air routes are maintained, thus making the drawing of certain standard runes easier.
And what kind of runes are being drawn in Earth’s skies, now? Nothing harmful. If you want to know more than that, well — there’s a price, which is that you’ll now know why they’re being drawn, which means that you’ve just volunteered to help guarantee that those runes keep getting drawn. Many people don’t want to sign up for that kind of responsibility, sight unseen. Do you?
There’s nothing like a conspiracy theory to hide an almost, but not quite, unrelated actual conspiracy.
For instance, a key element of the UFO/Conspiracy mythology was a genuine attempt to keep the Soviets from learning that the US was sending up high-altitude balloons which recorded low-frequency sounds echoing around the upper atmosphere. This was how the US monitored Soviet nuclear weapon tests in the late 1940s for a few years, until people realized that seismographs did a better job.