Chemtrails: Who is doing it and why?

[Into the Night]

Naw, they've been spraying stuff in the skies, seriously.

A contrail consists of carbon dioxide and liquid water.
It comes from the exhaust side of the engines.

Further, wingtip vorticies can form a trail when the aircraft is flying slow, such as on approach. These also leave a visible trail of liquid water. This phenomenon is particularly visible in cooler moist environments such as Seattle, particularly during approaches with low ceilings.

So, yes. Jet aircraft are spraying something into the skies. Carbon dioxide and liquid water.