Gallery 3 - Earth Bound   >   Clouds   >   Contrails

Contrails or vapour trails are long thin artificial clouds that can form behind aircraft. Their formation is most often triggered by the water vapour in the exhaust of aircraft engines, but can also be triggered by the changes in air pressure in wingtip vortices. Like all clouds, contrails are made of water and they can 'seed' large clouds . We are not sure if the large cloud in the photo is a contrail or a cloud that formed from the beginnings of a contrail. It was very unusual to see. Photo by Peter