Originally Posted by
El Bunto
FlyBE's Dashs and Loganair's 2000s seem to be able to hit trailling conditions occasionally. It makes me look every time, seems odd to see something moving slowish-ly and making a brrrr noise but pulling trails. I haven't yet seen an ATR doing so but they seem to top-out around FL170 which may not be sufficient.
There was a lot of work done during WWII to try, not entirely successfully, to model the conditions under which USAAF daytime B-17 raids on Germany would be particularly vulnerable when conditions resulted in them creating contrails.
It's still an inexact science.