Construction
Construction of the airfield began on 12 January 1942. The consulting engineers were Landon-Every And Ferkin Ltd. and the main contractor was Messrs A.M. Carmichael (Scotland).
Some of the best agricultural land in the area was taken. Compensation, considered by some to be totally inadequate, was offered, but not always accepted. In some cases households were asked to vacate their homes almost overnight. Some families refused to move and the airfield was built around them, in the townlands of Derryoge, Dunnaval, Ballynahatten, Cranfield, and Grange.
Air Ministry Compulsory Acquisition orders gave the occupiers three days to move out, without any obligation on the Air Ministry to find them alternative accommodation. This short notice period applied only to houses that were sited where the runways were to be built. Other home owners had more time to remove roofs and anything else that was salvageable. Most of the farmers had their lands cultivated and ploughed ready for the planting of early potatoes, an important crop in this area of small (5-15 acres) family farms. Sheds were full of boxes of sprouted Arran Pilots ready to be planted.
Around 450 buildings of various shapes and sizes were erected, at a safe distance from the ammunition and bomb stores, and runways. A number of building foundations were excavated and concreted but never built on; other buildings were only partly erected. Several new buildings were never used during the war years. Approximately 5 miles of water mains were was laid from the Silent Valley reservoir. Ownership of this pipeline was transferred to the local authority when the station closed.
Operations
The station was a satellite of RAF Langford Lodge (AAF Stn 597) and was established to handle the overflow from the extremely busy parent station.
From 1944 until the end of the war, salvage, refurbishment and repair of both 8th and 9th AF was carried out at both stations, as was the training of bomber crews. Air gunners were trained at RAF Greencastle by the USAAF where the 4th Gunnery & Tow Target Flight were located with Douglas A-20 Havocs, Westland Lysanders and Vultee Vengeance A-35B's in the Consolidated B-24 Liberator gunnery school.
May until August 1944 was classed as the busiest period of WW2; during July 1944, 330 heavy bomber crews graduated from Greencastle and Cluntoe.
The following RAF units were based at RAF Greencastle at various times:
