Planned as an RAF bomber OTU, Greencastle was built during 1941-42 and had three concrete runways, 30 pan type hardstandings and four T2 hangars. 50 more 'finger’ or 'Y’ type hardstandings were added in 1943. Allocated to the USAAF in 1942 as a bomber support or training base, it was not occupied until August 1943, and was used primarily as a satellite air depot to RAF Langford Lodge, for temporary storage of B-17s, B-24s and other types needed as replacements for Eighth Air Force bomber losses. Other important roles were ground training for bomber crews, particularly air gunners, and also of Anti-Aircraft gunners for airfield defence. Handed back to the RAF in May 1945, the station soon closed and has since largely returned to agriculture. The runways were broken up during the 1960s and used to construct boundary walls. The Control Tower and several other wartime buildings still exist, albeit in derelict condition.