After the U-boats were pulled back from the US east and gulf coasts they concentrated in an area called the Air Gap. This was a place in mid-Atlantic that could not be covered by aircraft. As the British improved their ASW techniques the Germans changed their submarine tactics as well. One aspect of ASW the German’s and American’s for that matter never could fully escape was aircraft.

The air gap was created simply because airplanes did not have the range they needed to cover the entire ocean. There was a gap in this coverage and this made for a perfect place for wolf packs to attack convoys. Even with surface escorts convoys were still vulnerable to attacks by wolf packs.

The gap continued to shrink during the war. By early 1943 the gap was small and concentrated. This gave the allies an area to concentrate their efforts with surface escorts, but it also gave the Germans a perfect spot to sink massive amounts of ships. The Battle of the Atlantic was still up for grabs at this point and either side could have earned a victory.

Closing the air gap was the key to winning the battle. May 1943 the air gap was officially closed. Long range aircraft along with escort carriers helped to make this a reality. After the gap was closed aircraft could escort convoys across the ocean and provide protection against U-boats, conditions allowing. Although aircraft could not escort at night or during bad weather the U-boats still needed time to surface and recharge batteries and stalk their prey. Aircraft limited this time and the U-boats suffered.