Escort carriers close the mid-Atlantic air gap

Why did escort carriers matter so much in the Battle of the Atlantic?

They extended air coverage into the mid-Atlantic gap, but producing them required finding hulls that could be spared from other urgent transport and fuel duties.

Wartime escort carriers followed earlier Royal Navy experiments with Argus, Hermes, and Eagle in anti-submarine and convoy-support roles. Convoy PQ 18 is an Arctic example of the type's wartime value. Converting suitable merchant hulls was not an automatic choice: fast liners were needed as troop transports, while tankers were carrying fuel. Leadership and institutional willingness to improvise influenced how quickly another type of hull could be selected. Aircraft could deny U-boats the relative freedom they had enjoyed beyond shore-based air cover.