Contrails (short for “condensation trails”) or vapor trails are long thin artificial (man-made) clouds that sometimes form behind aircraft. Their formation is most often triggered by the water vapor in the exhaust of aircraft engines, but can also be triggered by the changes in air pressure in wingtip vortices or in the air over the entire wing surface. Like all clouds, contrails are made of water, in the form of a suspension of billions of liquid droplets or ice crystals.
Depending on the temperature and humidity at the altitude the contrail forms, they may be visible for only a few seconds or minutes, or may persist for hours and spread to be several miles wide. The resulting cloud forms may resemble cirrus, cirrocumulus, or cirrostratus. Persistent spreading contrails are thought to have a significant effect on global climate.
The above pictured contrails are taken in Prague’s residential district Vinohrady, namely in Anglicka street.
(Above) Somewhat dispersed aircraft contrails behind no-longer visible planes. Picture taken in Jindrisska street in Prague.