Jet fuel also contains a lot (relatively) of water, which
condenses soon after leaving the exhaust. That is why they
are called CONTRAILS condensation trails. They were first
seen behind the bombers during WWII and so-named.


"Thomas Borchert" wrote in
message ...
| AliR,
|
| Is either one of us right?
|
|
| Your friend, partly. There are atmospheric conditions when
the pressure
| change over the wing or at a wing tip is enough to make
the water in
| the air visible. But they are rare and don't make long
contrails. The
| long contrails from jets you see are because the exhaust
contains small
| particles (soot and other stuff) which cause the water
vapor in the air
| to condense on them where it wouldn't condense without
them.
|
| --
| Thomas Borchert (EDDH)
|