Contrails are long and narrow traces of condensation caused by super saturation of water vapour. This is caused mostly by het exhausts, but there are cases when aerodynamic effects (wing tips or otherwise) contribute to contrail formation. They have a life time that varies between minutes and hours, and may evolve into high-altitude cirrus clouds. A considerable amount of research exists on this environmental problem.

Distrails are deep scars in the cloud system by aircraft flying at relatively low altitudes, mostly on final approach and landing. Distrails are less common and are not studied at the same level as contrails.