A visual approach is an approach to a runway at an airport conducted under instrument flight rules (IFR) but where the pilot proceeds by visual reference and clear of clouds to the airport. The pilot must at all times have either the airport or the preceding aircraft in sight. This approach must be authorized and under the control of the appropriate air traffic control (ATC) facility.[1] The International Civil Aviation Organization (ICAO) definition adds that the visual approach can commence when "either part or all of an instrument approach is not completed", varying only slightly from the Federal Aviation Administration regulation and is essentially identical.[1]