Stratiform and stratocumuliform clouds in the topmost region of the troposphere have the prefix "cirro-" added to their names yielding the genera cirrostratus and cirrocumulus.
The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.
However, contrails formed from the exhaust of high-flying aircraft can persist and spread into formations resembling cirrus, cirrocumulus, or cirrostratus.
