The Shannon Estuary () is a large estuary where the River Shannon flows into the Atlantic Ocean. The estuary has Limerick City at its head and its seaward limits are marked by Loop Head to the north and Kerry Head to the south. The estuary defines the main boundary between County Kerry/County Limerick to the south and County Clare to the north. The length of the Shannon Estuary is . The Lower River Shannon Special Area of Conservation (SAC) incorporates the estuary and is in length, running from Killaloe to Loop Head. The Shannon has a high tidal range, up to around at Limerick docks, such that the estuary has been considered for tidal power schemes, despite occasionally experiencing a tidal bore. In the second half of the 19th century about 65 km² of the estuary's lowlands have been embanked and reclaimed, largely for agricultural purposes. Aircraft In the late 1930s, transatlantic air traffic was dominated by flying boats, and a flying boat terminal was located at Foynes on the south side of the Shannon Estuary. However, it was realised that developing technology would require a permanent runway and airport. In 1936, the government of Ireland confirmed that it would develop a site at Rineanna for the country's first transatlantic airport. The land on which the airport was to be built was bog, and on 8 October 1936 work began to drain the land. By 1942 a serviceable airport had been established and was named Shannon Airport. From then, passengers were moved from the flying boats in Foynes to the land planes based at Shannon Airport. By 1945 the existing runways at Shannon were extended to allow transatlantic flights to land, completely bypassing the need for Foynes. Port Shannon Foynes Port Company is the port authority for the entire estuary. It owns facilities at Foynes Dock, Limerick City and at airport jetty. It provides marine services, including pilotage and towage to privately owned facilities at Moneypoint, Tarbert Island and Aughinish. The maritime history of the estuary is catalogued and on display in exhibits at the Maritime Section of the Foynes Flying Boat Museum Sustainable exploitation The Shannon Estuary is an immensely important asset and one of the most valuable natural resources in Ireland and the Mid-West Region in particular – the fringe lands and the marine area both provide space and location for development activities and opportunities to progress economic,