Why do planes create holes in the clouds?

The mysterious cloud hole is the result of supercooled droplets freezing into ice crystals in a chain reaction, according to Sci Tech Daily. About 8% of Earth’s sky is covered by mid-altitude stratus clouds such as altocumulus and altostratus, which appear as multiple horizontal layers.

Sometimes, especially near winter flyworms, these clouds develop an unusual feature in which the base appears to fall away. The phenomenon that creates a characteristic shape is called a cloud hole. On December 2, 2024, the OLI-2 (Operational Land Imager-2) imager on the Landsat 9 satellite took pictures of two cloud holes in the sky above Wichita, Kansas. Seen from above or below, a cloud hole looks like a neatly cut circle or a cloud-covered eclipse. Their centers often have thin strips of cloud, which look as if clouds are pouring from the sky.

The phenomenon occurs in mid-level clouds containing super-strong water droplets that remain liquid even below 0 degrees Celsius. But even super-cooled drops can freeze. When an airplane flies through a layer of clouds, the extra cold above the wings can push the supercooled liquid droplet to a frozen state. Ice crystals become heavier and fall, leaving gaps in the cloud. Falling ice crystals often appear as sparse rain streaks called virga.

Researchers looking at major airports around the world estimate that atmospheric conditions are suitable for cloud holes to form 3 to 5 percent of the time, but increases to 10 to 15 percent of the time in winter. The plane flew past at an acute angle, creating a small circular cloud hole. At more obtuse angles, the plane creates long clouds with widespread rain streaks. Other factors that can influence the length of a cloud hole include the thickness of the cloud layer, air temperature and the degree of wind shear.