Contrails – formation, type and classification


Under certain atmospheric conditions, visible trails form behind aircraft in the sky. These condensation trails, or contrails, mainly consist of water in the form of ice crystals and are created by the combination of atmospheric humidity and low temperatures at cruising altitude.

Contrails appear in various forms. The natural conditions at cruising altitude determine how contrails appear and how long they last.

Hundreds of photos and videos can be found online showing all different types of contrails. Their appearance is often linked to a conspiracy theory claiming that aircraft spray chemicals to manipulate the weather, to reduce the population or for military purposes. The proponents of such theories incorrectly interpret these natural occurrences, which they call chemical trails or chemtrails.

Contrails can actually form cirrostratus clouds and influence the climate but their occurrence is based on the laws of physics. The FOCA factsheet provides an overview of the key points.

Further Information

Last modification 17.10.2023

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