 The YB-40 project failed because the aircraft were able to effectively defend only themselves, were too slow because of excess weight and drag to keep up with bomber formations returning from missions, and had basic flight characteristics altered by the added drag and centre of gravity changes resulting from the changes.After 14 operational missions, the 11 surviving YB-40s were taken out of combat service and returned to the United States.On 15 September 1943, the 92d BG was moved to RAF Podington (Station 109), near Wellingborough in Bedfordshire when the decision was made to take Alconbury off operational bombing missions and change the airfield's mission to pathfinder and radar-guided bombing with the 482d and 801st Bomb Groups.