"I have examined the mathematics presented in [article] in detail and have concluded they are correct. Two fixed-wing anti-submarine aircraft operating together are six times as effective as one working alone. Three fixed-wing anit-submarine aircraft working together are twice as effective as two working together. In my mind, however, 12 times 0 is still a very small number".

From Proceedings of the U.S. Naval Institute, a couple of decades ago. If anything has changed since, I think it's in favor of the submarines.