The International Civil Aviation Organization (ICAO) defines civil aviation aircraft operations in three categories: General Aviation (GA), Aerial Work (AW) and Commercial Air Transport (CAT). General aviation thus represents the 'private transport' and recreational components of aviation. It also includes activities surrounding aircraft homebuilding, flight training, flying clubs, and aerial application, as well as forms of charitable and humanitarian transportation. Private flights are made in a wide variety of aircraft: light and ultra-light aircraft, sport aircraft, business aircraft (like private jets), gliders and helicopters. Flights can be carried out under both visual flight (VFR) and instrument flight (IFR) rules, and can use controlled airspace with permission.