Shannon Airport (Irish: Aerfort na Sionainne) (IATA: SNN, ICAO: EINN) is an international airport located in County Clare in Ireland. It is adjacent to the Shannon Estuary and lies halfway between Ennis and Limerick. With almost 2 million passengers in 2023, the airport is the third busiest airport in the Republic of Ireland, and the fifth busiest on the island of Ireland. Shannon has had a long association with transatlantic flight, owing to its position on the west coast of Ireland and being one of the most westerly international airports in Europe. One half of Shanwick Oceanic Control, which controls all air traffic on the north eastern quadrant of the North Atlantic Ocean is located close to the airport in nearby Ballygirreen. The airport was built in the late 1930s, with the first commercial flight taking place in 1939. Shannon was the landing point for the first transatlantic proving flight in 1945 and became the world's first duty-free airport in 1947.