General aviation in the United Kingdom has been defined as a civil aircraft operation other than a commercial air transport flight operating to a schedule or military aviation. Although the International Civil Aviation Organization (ICAO) excludes any form of remunerated aviation from its definition, some commercial operations are often included within the scope of general aviation (GA) in the UK. The sector operates business jets, rotorcraft, piston and jet-engined fixed-wing aircraft, gliders of all descriptions, and lighter than air craft. Public transport operations include business (or corporate) aviation and air taxi services, and account for nearly half of the economic contribution made by the sector. Other commercial GA activities are aerial work, such as surveying and air ambulanc