Ominous for BdU was the sudden growth of Allied air power. The Allied command accepted that air cover over the mid-Atlantic was totally inadequate and had drawn attention to the fact that not one VLR (Very Long Range) aircraft was to be found at any Allied air base west of Iceland. The Americans released 255 Liberators for the North Atlantic. At the end of March 1943 20 VLR aircraft were operational rising to 41 by mid-April, all of them flown by British crews. 28 anti-submarine and 11 anti-shipping squadrons were available to RAF Coastal Command, 619 aircraft in all—a striking change since September 1939. The influx of radar equipped aircraft into mid-Atlantic was matched by air patrols over the Bay of Biscay. Dönitz detected a drop in morale among his captains, as did the British. Dönitz encouraged his commanders to show a "hunter's instinct" and "warrior spirit" in the face of the air–surface support group threat.