Aldergrove was already established in 1918 as a RAF training camp. It had its own squadron based there, the No. 502 (Ulster) Squadron, RAF Special Reserve, which formed in 1925. The lough was used as a firing range for bombing and gunnery practice, the targets being set by fishermen local to the nearby shore and replaced by the same when necessary. In 1920 civilian flights were operated from Aldergrove but they were intermittent. The first regular air services in Northern Ireland did not began until 1933, commencing with the route between Glasgow to Aldergrove. This was short lived though as the newly constructed Nutts Corner took over civilian flights from Aldergrove beginning in 1934 with the first flight service from London. This arrangement lasted until the outbreak of WWII when civilian flights, though largely abandoned, were transferred to Belfast Harbour Airport (now the George Best Belfast City Airport). In 1946 civil air operations were transferred back to RAF Nutts Corner due to the longer runways available at that airfield and limited space at Belfast Airport. Also the shipyard cranes within the harbour area proved an unnecessary hazard. After this Nutts Corner airfield became known as Belfast-Nutts Corner Airport.
In July 1959 the steep approach necessary for aircraft flying to Nutts Corner was deemed unsuitable due to its location so close to the Belfast Mountains and the fact that only one of the three runways was suitable for modern civilian aircraft. Aldergrove on the other hand was closer to the Lough shore and had two runways set at 100 degrees to each other which allowed for take-off and landing in all wind directions. In October 1963 the Belfast International Airport opened at Aldergrove.