|Montana Contrail Shadow imaged by James Perdue at Culver Pond in Red Rock Lakes National Wildlife Refuge. Image ŠJames Perdue, shown with permission.
The high contrail comprised of water droplets and possibly ice crystals has cast a shadow deep down into the atmosphere. The shadow is a 3D volume of dark air. In contrast, many contrail shadows cast onto lower cloud or haze layers are 2D.
More contrails below...