Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing.
Wingtip vortices are associated with induced drag, an unavoidable side-effect of three-dimensional lift generation. Careful selection of wing geometry (in particular, aspect ratio), as well as of cruise conditions, allows reducing induced drag by controlling the vortices’ influence on the wing.
Wingtip vortices form the major component of wake turbulence. Depending on ambient atmospheric humidity as well as the geometry and wing loading of aircraft, water may condense or freeze in the core of the vortices, rendering them visible.
Wingtip vortices are sometimes named trailing or lift-induced vortices because they also occur at points other than at the wing tips. Indeed, vorticity is shed at any point on the wing where the lift varies span-wise (a fact described and quantified by the lifting-line theory); it eventually rolls up into large vortices near the wingtip, at the edge of flap devices, or at other abrupt changes in wing planform.
Read more about Wingtip Vortices: Generation of Trailing Vortices, Effects and Mitigation, Visibility of Vortices, Formation Flight, Hazards, Gallery