They don’t exist. Period.
There’s not a shred of evidence to support the idea that someone nefarious is putting something nefarious in Jet A fuel so that, once burned in a jet engine, it will float down on us and render us sterile, zombies or passive. So, what are we seeing? What we’ve always seen: contrails. It’s the water vapor that is condensing and freezing almost instantly as it’s thrust out of the back of a jet engine. Depending on the weather conditions up there, we either see a bunch of them or we see nothing. Believe me, the planes are there every day, crisscrossing Arizona. Pick up one of those “flight follow” apps and you’ll be amazed how many aircraft are in the sky.
So, why do we see contrails some days and not on others? It really depends on the conditions of the atmosphere the jet is flying through. Check out this video of a jet producing a HUGE contrail.
Now here’s the part that’s really interesting and science. On many days, contrails can persist for hours and, yes, spread out into other clouds. Contrails are playing a role in our climate, probably warming the planet. Basically, contrails reduce the “spread” of temperatures on an average day, especially at night. On the days following Sept. 11, 2001, when there were virtually no aircraft in the air, meteorologists noted that nighttime temperatures all of a sudden were running cooler with no other weather systems playing a part in that. Also, we still don’t have a very good understanding of what putting all that jet exhaust in the atmosphere is playing in our long-term climate. Probably, it’s not a very good impact.
So, there are no chemtrails as expressed by the many conspiracy theories of our day but we do have contrails, and those contrails are playing a role in our daily weather and, perhaps, long-term climate change as well.