Years ago I read somewhere on You Tube about chemtrails, that some pilots spraying the trails used to call the X’s in the sky for extermination signs. It was a kind of internal professional's joke!
Anyway - on newspeek.info is an article about questions to the Danish Meteorological Institute regarding geoengineering and spraying from chemtrails. There is also a response from DMI.
https://newspeek.info/lene-bang-i-korrespondance-med-danmarks-meteorologiske-institut-dmi/