Police aviation is the use of rotary-wing aircraft, fixed-wing aircraft, nonrigid-wing aircraft or lighter-than-air aircraft in police operations. Police services commonly use aircraft for traffic control, ground support, search and rescue, high-speed car pursuits, observation, air patrol and control of large-scale public events and/or public order incidents. In some major cities, police rotary-wing aircraft are also used as air transportation for personnel belonging to SWAT-style units. In large, sparsely populated areas, fixed-wing aircraft are sometimes used to transport personnel and equipment.