wrote in message
news:3J29i.3772$jW6.3719@trnddc01...
It's not just jets. WW2 bombers, B17s and the like, also left contrails
when they were on high altitude runs. Combustion produces water vapor,
which under the right conditions condenses into a cloudlike trail of
visible water droplets.

Actually ice crystals.

Contrails (water vapor condensation) can also form in wingtip vortices or
propeller tips especially when pulling high G loads (high angle of attack
accelerated turns) IIRC they happen in these contexts as the low pressure
area over the wing (or prop) grows and the low pressure air can't hold as
much water vapor as higher-pressure air can, so the relative humidity
increases eventually to 100% of capacity at which point the H2O vapor
condenses out as droplets.

Mike


Correct except that's not a contrail, just vapor created as you described.

Rob