A procedure for bringing an aircraft to land by non-visual means. Approaches are precise flight patterns designed to steer the aircraft away from any land-based obstacles, as well as to control the flow of aircraft into the airport. The procedures are guided by position fixes obtained from one or more radio navigation aids, such as a VOR, ILS, NDB, or more recently GPS.
Approaches may be classified as precision or nonprecision. The former includes some form of guidance in the vertical plane, while the latter relies on time, speed and descent rate to establish glidepath.