"Homomutatus(Section 2.1.3.6.4) Persistent contrails (Cirrus homogenitus) may be observed, over a period of time and under the influence of strong upper winds, to grow and spread out over a larger portion of sky, and undergo internal transformation such that the cloud eventually takes on the appearance of more natural cirri-form clouds. In this instance, the resulting clouds will be given the name of the appropriate genus (for example, Cirrus, Cirrocumulus, or Cirrostratus) followed by any appropriate species, variety and supplementary features, followed by the special cloud name “homomutatus”, (for example, Cirrus floccus homomutatus or Cirrus fibratus homomutatus)." https://cloudatlas.wmo.int/homomutatus.html
Persistent aircraft condensation trails (contrails) cross the sky over southern England, UK. These are classified as Cirrus Homogenitus.
Because new or recently formed aircraft condensation trails may display a variety of transient shapes (seen at 2, 3 and 4), no species, varieties or supplementary features are used in the classification." https://cloudatlas.wmo.int/imgviewer-5201.txt
"Aircraft condensation trails(Section 2.1.3.6.3) Aircraft condensation trails (contrails) that have persisted for at least 10 minutes will be given the name of the genus, Cirrus, followed only by the special cloud name “homogenitus”, so a contrail will be known only as Cirrus homogenitus. As new, or recently formed aircraft condensation trails may undergo a fairly rapid state of change and may display a variety of transient shapes, no species, varieties or supplementary features will be applied to the name." https://cloudatlas.wmo.int/aircraft-condensation-trails.html
