Wake turbulence is the phenomenon of disturbed airflow; i.e., wing-tip vortices, created behind an aircraft's wing as the aircraft moves forward.

Note: Wake turbulence can be a serious hazard to lighter aircraft following heavier aircraft.

Wake vortex turbulence is present behind every aircraft, including helicopters, when in forward flight. It is extremely hazardous to a lighter aircraft with a smaller wingspan during takeoff, initial climb, final approach (including the circuit), and landing phases of flight following a heavier aircraft with a larger wingspan.

Note: Wake turbulence also can be encountered in the cruise but is not really a hazard, just an uncomfortable disturbance.

The characteristics of the wake vortex turbulence generated by an aircraft in flight are determined initially by the aircraft's gross weight, wingspan, airspeed, configuration, and attitude. That is, a heavy aircraft with a large wingspan creates the greatest wake turbulence (wing-tip vortices) because it creates the greatest pressure differential between the upper and lower surfaces of the wing. The wake turbulence created from trailing wing-tip vortices can be strong enough to upset a following aircraft, especially a lighter aircraft, if it flies into them. To avoid wake turbulence accidents and incidents, air traffic control (ATC) delays the operation of lighter aircraft behind heavier aircraft for up to 5 minutes to allow the vortices that create the wake turbulence to dissipate.

Note: Aircraft of the same size or heavier aircraft following lighter aircraft do not suffer from dangerous levels of wake turbulence and therefore are not usually spaced as per International Civil Aviation Organization (ICAO) separation minima.