Contrails

[Kevin McDole]

FWIW: I don't know much about contrails, but I can use a search engine.

Contrail Forecasting:
http://www-pm.larc.nasa.gov/sass/con...rediction.html

Contrails can be formed by propeller or jet turbine powered aircraft.
http://www.af.mil/environment/contrails_contrail.shtml

The usual temperature range for the formation is -34°C and -40°C. Between the ice saturation level and near ice saturated conditions in conditions which are cirrus clouds do not usually form.:
http://www.lancs.ac.uk/postgrad/ledson/project.htm