NOx
Just a small correction to Specnut...
The NOx doesn't come from inefficient combustion, it is part of the 80% or so in the atmos which, under the high temp/pressure environment inside the jet engine, reacts with the Oxygen - and it gets blown out the back end. Other than that a great explanation.
Inefficient combustion will indeed lead to CO and soot (brown/black exhaust trails), but I would have thought that there would be a vast excess of oxygen in the jet engine, so if that is happening it must be poor vaporisation of the fuel