H2O

Water.

It has very distinctive properties that are unusual in most chemicals.

That's why it forms clouds in the sky.

You see under the right conditions persistent contrails that go from horizon to horizon for and sometimes spread out into clouds. To make one takes a mind boggling amount of material. Truth is the concept that so-called chemtrails are "sprayed" is patently ridiculous.

Have you seen videos of fire fighting aircraft releasing their loads? How about aircraft that dump their entire load of fuel? The dump takes mere seconds and then that's all she wrote. Simply put, these aircraft just cannot carry the amount of material to "spray" so-called chemtrails from horizon to horizon.

Another Fact is that fine particulate aluminum, barium, whatever, would not appear as dense contrails if released at altitude.

Simply put those trails you see? They are made up of water that has changed state. Water that was already in the air as the aircraft passed through it. Sure a little of it is from the fuel being burned and some carbon aerosol is also created that is a catalyst that makes the other moisture in the supersaturated air change state.

Anyway, that is the basic process that is happening.

Persistent contrails were first seen during the last year of World War One. They have been seen, documented and discussed ever since then.