An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports often have facilities to store and maintain aircraft, and a control tower. An airport consists of a landing area, which comprises an aerially accessible open space including at least one operationally active surface such as a runway for a plane to take off or a helipad, and often includes adjacent utility buildings such as control towers, hangars and terminals. Larger airports may have airport aprons, taxiway bridges, air traffic control centres, passenger facilities such as restaurants and lounges, and emergency services. In some countries, the US in particular, they also typically have one or more fixed-base operators, serving general aviation.
An airport solely serving helicopters is called a heliport. An airport for use by seaplanes and amphibious aircraft is called a seaplane base. Such a base typically includes a stretch of open water for takeoffs and landings, and seaplane docks for tying-up.
An international airport has additional facilities for customs and passport control as well as incorporating all of the aforementioned elements. Such airports rank among the most complex and largest of all built typologies with 15 of the top 50 buildings by floor area being airport terminals.