A distrail, short for dissipation trail, forms when an aircraft flies through a supercooled cloud. The cloud freezes due to the disturbing airflow created by the aircraft, as well as by the addition of plenty of freezing nuclei due to the aircraft's exhaust gases. Altocumulus is usually either frozen or supercooled and can show distrails. They are uncommon, especially the clear distrails. Distrails are usually not very long, since they usually show in altocumulus which is not at a cruising altitude of the aircraft (i.e. the aircraft is either descending or ascending through the cloud). In some cases a distrail may transform into a cloud hole: a large elliptical hole in altocumulus with virga in the middle.
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