
For fuck's sake, it's CONtrails. From CONdensation i.e. water vapour.
( , Wed 18 Jul 2012, 1:18, Reply)

They generate smoke by spraying something into the exhaust (may be kerosene, not sure right now). It all evaporates long before it gets to ground level though.
( , Wed 18 Jul 2012, 11:14, Reply)