>contrails
>smoke
REE
The contrail is a cloud of ice crystals formed due to both the humidity created from engine exhaust (a byproduct of combustion is H20), the relative humidity increasing (due to the temperature rise created from the hot exhaust) to the point where the air becomes saturated and visible moisture appears. Since temperatures around the troposphere/low stratosphere hang around -57°C the water vapor freezes instantly, creating a trailing cloud of ice.
