RAF Thurleigh was built in 1940 for RAF Bomber command. It was used by both 160 Squadron RAF and then by the RAF No.18 Operational training unit, before being transferred to the United States Army Air Forces on 9 December 1942 who used it for heavy bomber operations against Nazi Germany which necessitated the lengthening and strengthening of the runways in order to accommodate the combat weight of the B-24 bombers. With the essential construction completed, the 306th Bombardment Group (Heavy) deployed to Thurleigh on 7 September 1942 from Wendover AAF Utah. The group struck locomotive works at Lille, railway yards at Rouen, submarine pens at Bordeaux, shipbuilding yards at Vegesack, ball-bearing works at Schweinfurt, oil plants at Merseburg, marshalling yards at Stuttgart, a foundry at Hannover, a chemical plant at Ludwigshafen, aircraft factories at Leipzig, and numerous other targets on the Continent. The 306th Bomb Group flew its 342nd and final mission on 19 April 1945, the most of any Eighth Air Force B-17 unit except the 303rd Bomb Group. It compiled 9,614 sorties; dropped 22,575 tons of bombs; and had 171 B-17’s fail to return from missions.
Starting in 1946, construction work began on the airfield to turn the site into what became known as the Royal Aeronautical Establishment, Bedford. The runway was extended again in the post-war period to accommodate the Bristol Brabazon aircraft that ultimately never went into production. One local road was dropped into a cutting so that it would not sit above the level of the runway. The airfield was decommissioned in February 1994 and closed in 1997 after a lengthy study determined that flight operations should be centralised at Boscombe Down in Wiltshire. The RAE became the Defence Evaluation and Research Agency (DERA). Due to the cost and impracticality of relocating the Advanced Flight Simulator system the site retained some of its development work until 2007 under the banner of QinetiQ.