a manual particle collector (broom) and a manual particle shifter (shovel).

Harks back to the Viet Nam war. We had to destroy the village to save the village. I believe this is the one where the Pulitzer prize winning photo of the naked little girl running with massive burns from napalm happened.

In answer to your question: yes. Humid cold pure air. By pure, I mean no contaminates until the hyrdrocarbons from the jet fuel are emitted into that pure, moist air. To form a droplet, a nucleus is needed. The hydrocarbons of the jet engine exhaust provide that nuclueus.

Well, it’s impossible to ban natural clouds but planes could avoid making contrails by just not flying in the zone where their exhaust would cause them. Source: I was a weatherman in the Air Force and would tell military pilots where to fly to not have a shiny line pointing to their exact location if such information could be a concern.

I never thought it about as a green house thing before though I do remember reading an article many years ago that contrails do contribute when they spread out into cirrostratus clouds.

I was a meteorologist in the Air Force and did make forecasts telling pilots at what levels to fly to avoid making contrails since having a long silver line pointing to your exact location makes sneak attacks a little difficult. Perhaps commercial airlines should make use of that information. It’s usually just a few thousand foot difference. Fly a little higher or lower and problem solved.