Wingtip vortice patterns in smoke from flares. The plane at upper right, a C-17 Globemaster III from the US Air Force, released a series of flares to form the smoke pattern seen here. The two vortices (circular patterns, upper centre) are caused by air spiralling off the tip of the airplane's wings. The resulting pattern is known as a smoke angel. Photographed over the Atlantic Ocean in May 2006.