Carrier aircraft create a moving anti-submarine corridor

Aircraft conducted anti-submarine warfare before carriers took on the mission during the interwar years. Land-based patrol coverage thins as distance from the airfield increases and eventually stops at the aircraft's range limit. A carrier moves the airfield with the convoy or task group, creating a corridor of relatively constant aircraft density around the formation. Early submarines spent much of their time on the surface and were slow underwater, consuming limited oxygen while submerged. Making one dive could therefore achieve a temporary mission kill by allowing the protected ships to pass, even though the submarine could return to action later.