like Fishona, i know the term contrails but i don't think i have ever spoken it.. i speak of vapor trails.

they are more common nowdays, i remember when 90% of transatlantic flights stopped for a final refueling at boston, (Non stops direct from NY to most parts of europe were not common in the early 1960's)-- Now, you can go Nonstop from paris to chicago! (and farther i am sure.. i just don't fly in or out of chicago, so i don't much think about it)