What are airports?

ICAO defines an aerodrome as an area intended wholly or partly for the arrival, departure and surface movement of aircraft. An airport is an aerodrome open to public traffic with buildings and services for passengers and cargo. The difference matters: a grass strip at a flying club is an aerodrome, but not an airport. Each one receives a four-letter ICAO code (LEMD for Madrid-Barajas) and, if it has commercial traffic, a three-letter IATA code (MAD).

The airside covers everything aircraft touch. Runways are numbered according to their magnetic heading in tens of degrees: runway 27 points to roughly 270°. Their length ranges from 1,500 m at a regional airport to more than 4,000 m at hubs operating wide-body aircraft at maximum load. Taxiways link the runway and the apron, where aircraft park, refuel and board passengers. The control tower manages movements on the ground and in the traffic pattern, while navigation aids and approach lights allow operations in poor visibility.

The landside comprises terminals, access roads, parking and the areas before the security checkpoint. That checkpoint, and on international flights passport and customs control, separate both worlds. Large airports function like cities: they handle tens of millions of passengers a year and have their own fire brigades, power plants and deicing crews. Their management can be public, private or mixed, but operational safety is governed in all cases by ICAO Annex 14 and the national aviation authority.