In the 46 months following July 1940, German aircraft sank 1,228, 104 tons of merchant shipping and damaged 1,953, 862 tons. Another 60, 866 tons were sunk or damaged by mines in 1942 and 1943. The failure to properly cooperate with the navy against shipping was a grave strategic error which prevented the achievement of greater results. Göring's intransigence was large factor in reducing the air effort. In May 1942, "Fliegerführer Atlantik" had only 40 aircraft and IX. Fliegerkorps, under Sperrle's command at Soissons, 90. The U-boat arm continued to press for greater air protection in the Bay of Biscay. In 1942, anti-shipping operations near the British coast proved too expensive, and the demands of the Mediterranean Theatre and Eastern Front diverted some of the precious Focke-Wulf Fw 200s. These aircraft would not return for Atlantic operations until the summer, 1943.