RAF Bomber Command night time sorties during Big Week[14] Date Notes 19/20 February 1944 921 sorties, 79 aircraft (8.6%) lost. The major raid, by 823 aircraft, was to Leipzig; (B-17s of the U.S. VIII bombed Leipzig-Mockau Airfield earlier the same day) but it suffered as fighters had not been drawn off by diversion raid on Kiel. de Havilland Mosquitos bombed nightfighter airfields in the Netherlands and a further 15 made a diversionary raid on Berlin.[14] 20/21 February 826 sorties, 10 aircraft (1.2%) lost.