Drawings of Contrails - White Lines Across the Sky
Contrails are vapor trails that form from the exhaust created by a plane's engines, and they can also form when the plane moves through a change in air pressure. Depending on the conditions, contrails can disappear in a few seconds or eventually become clouds.
These days, they're a less common sight due to the drop in air travel. But you'll always be able to see them on pixiv!