Dublin Airport, (Irish: Aerfort Bhaile Átha Cliath) (IATA: DUB, ICAO: EIDW), is an international airport serving Dublin, the capital city of Ireland. It is operated by daa. The airport is located 5.4 nmi (10.0 km; 6.2 mi) north of Dublin and it is located in Collinstown, in County Dublin. In 2014, 21.7 million passengers passed through the airport, making it the busiest of the state's airports by total passenger traffic. It also has the greatest traffic levels on the island of Ireland followed by Belfast International Airport, County Antrim. The airport has an extensive short and medium haul network, served by an array of carriers as well as some intercontinental routes focused in the Middle East and North America. It serves as the headquarters of Ireland's flag carrier – Aer Lingus, regional airline Stobart Air, Europe's largest low-cost carrier – Ryanair, ASL Airlines Ireland, together with a fifth airline, CityJet, which doesn't maintain major operations here. United States border preclearance services are available at the airport for US-bound passengers. Shannon Airport is the only other airport in Europe to offer this facility.
In 1936 the Executive Council of the Irish Free State established a new civil airline, Aer Lingus, which began operating from the military aerodrome, Casement Aerodrome, at Baldonnel to the southwest of Dublin. A decision was made that a civil airport should replace Baldonnel as Dublin's airport The townlands of Collinstown, Rock and Corballis in the Barony of Coolock were selected as the location for the new civil aerodrome. Collinstown's first association with aviation was as a British military air base during World War I, but that field had been unused since 1922. Construction of the new airport began in 1937. By the end of 1939, a grass airfield surface, internal roads, car parks and electrical power and lighting were set up. The inaugural flight from Dublin took place on 19 January 1940 to Liverpool. In August 1938, work began on a new airport terminal building. The terminal building was designed by architect Desmond FitzGerald, brother of politician Garret FitzGerald. It opened in early 1941, with its design heavily influenced by the bridges of the luxury ocean liners of the time. The terminal was awarded the Triennial Gold Medal of the Royal Hibernian Institute of Architects, and is today a listed building. An Aer Lingus DC-3 plane at Dublin Airport's original Terminal 1 in May 1950. Upon the outbreak of World War II, services were severely restricted at Dublin Airport until late 1945 and the only international scheduled route operated during this time was by Aer Lingus to Liverpool (and for a period to Manchester's Barton Aerodrome). Three new concrete runways were completed by 1947.