Low level contrails, warm air/wings meets &
cuts thru, much more dense colder & water rich air,
a lot of water grains/content 70/per billion or much more
it doesn't have to cold either...
I've seen them on 105* days a ground level...
Top Fueler's
F1
A bit higher up altitude,
jet exhaust hitting
cold dense air at altitude,
makes vapor trails, nothing really new,
not poison well except maybe the exhaust CO2
or not some weird or nefarious CIA secret BS
Albeit they have done cloud seeding here,
we don't get much rain some years, have a ton of farming/agriculture,
It's burning aluminum/magnesium nitrate or something like that,
I'd have to look it up {chem.}, again it's not some secret nefarious stuff,
they've been doing it for a long time, over the summits, for Snow pack...