I’m sure many readers have seen, either in real life or in pictures, the trails of condensation left by aircraft as they move at high speed. They usually come from the wingtips or other prominent features that leave distinctive patterns of disturbed air, which are highlighted in humid conditions. They’re known as ‘wingtip vortices‘.
The same effect produces the circular, coil-spring-like condensation patterns sometimes left by aircraft propellers. Here’s a great example, produced by a Lockheed Martin MC-130J Commando II on its delivery flight from the manufacturer to Cannon AFB in New Mexico.
The image is from Lockheed Martin’s Flickr photostream. The full-size version makes great wallpaper for your computer screen.