Shanwick is the air traffic control (ATC) name given to the area of international airspace which lies above the northeast part of the Atlantic Ocean. The Shanwick Oceanic Control Area (OCA) abuts Reykjavík OCA to the north, Gander OCA to the west and Santa Maria OCA to the south. Shanwick also has eastern boundaries with the Scottish, Shannon, London, Brest and Madrid domestic ATC flight information regions. History Responsibility for the provision of air traffic services within international airspace is delegated to United Nations member states by the International Civil Aviation Organisation (ICAO). ICAO divides such airspace into flight information regions, parts of which may be deemed controlled airspace and, where appropriate, classified as an Oceanic Control Area. Prior to 1966, both the United Kingdom and Ireland were selected by ICAO to provide control and communications services to air traffic within adjacent areas of the north east Atlantic. The air/ground High Frequency (HF) radio communication station at Ballygirreen, near Shannon, County Clare, Ireland, provided HF communications to the Irish Aviation Authority ATC centre at Shannon. The HF radio communication station at Birdlip, Gloucestershire, England, provided HF communications to the Civil Aviation Authority (now NATS) ATC centre at Prestwick, Ayrshire, Scotland. The resulting duplication of work between ATC providers resulted in an agreement being reached between the UK and Irish governments, where Birdlip and Ballygirreen would work as a single unit. The Prestwick Centre assumed the control function of the joint area and Ballygirreen ultimately assumed sole responsibility for HF communications. The name Shanwick is a portmanteau of Shannon and Prestwick. Operation Responsibility for providing an Air Traffic Control Service (Including Flight Information Service and Alerting Service) to aircraft in receipt of a procedural control or ADS-B surveillance service falls to the Prestwick Centre, which also provides CPDLC and ADS-C services for suitably equipped aircraft. Voice radio communications are shared between the CDOs (clearance delivery officers) based at Prestwick Centre and the Irish Aviation Authority (IAA) Radio Operators from Shannon Aeradio, based in Ballygirreen. Shanwick Control further delegates control of traffic within the NOTA (Northern Oceanic Transition Area) and the SOTA (Shannon Oceanic Transition Area) to Shannon Control, and traffic in the Brest Oceanic Transition Area (BOTA) to Brest Control. Ballygirreen establishes radio contact with flights within the Shanwick OCA by means of HF radio, using the radiotelephony callsign "Shanwick Radio". HF can provide global coverage due to its ability to