Cirrus aviaticus
Family A
Genus Cirrus
Occurrence Worldwide
Altitude usually high altitudes (>5000 m) but dependent upon humidity
Formation Aircraft operations at high levels combined with significant moisture in the surrounding air
Precipitation None
Potential Hazards Indicates an approaching frontal system if long-lasting

Cirrus aviaticus trailing from a jet.

Cirrus aviaticus, commonly known as a contrail or vapour trail, is a cloud formation which form due to pressure and temperature changes caused by aircraft jet engines in the surrounding air. Usually, cirrus aviaticus dissipates quickly, but it can remain visible for long periods of time and even spread given the right atmospheric conditions.

High Clouds (Family A): Cirrus (Ci) • Cirrus aviaticus • Cirrus intortus • Cirrus radiatus • Cirrus uncinus • Cirrus Kelvin-Helmholtz • Cirrostratus (Cs) • Cirrocumulus (Cc) • Pileus • Contrail
Middle Clouds (Family B): Altostratus (As) • Altostratus undulatus • Altocumulus (Ac) • Altocumulus undulatus • Altocumulus mackerel sky • Altocumulus castellanus • Altocumulus lenticularis
Low Clouds (Family C): Stratus (St) • Orographic stratus • Fog • Nimbostratus (Ns) • Cumulus humilis (Cu) • Cumulus mediocris (Cu) • Stratocumulus (Sc)
Vertical Clouds (Family D): Cumulonimbus (Cb) • Cumulonimbus incus • Cumulonimbus calvus • Cumulonimbus with mammatus • Cumulus congestus • Cumulus castellanus • Pyrocumulus  • Pyrocumulonimbus