Plane used to fight against U boats?

WWII: PBYs, Wildcats, Hellcats, Corsairs would bomb and strafe enemy subs; these were launched from "baby flattops" (CVEs-ESCORT Carriers; the smallest aircraft carriers of WWII). The larger LIGHT and FLEET Carriers were kept in the Pacific.

Ans 2 - In the Pacific where the US Navy had many carriers, the smaller fighter and bomber aircraft had some success against submarines, but far more were sunk by patrol ships and destroyers.

In the north Atlantic it was a far different story. Here the Royal Air Force Coastal Command made very determined efforts at anti-submarine warfare. Using heavy, long range patrol aircraft such as Sunderland, Catalina(PBY) Liberator (B-24) and Hudson against German submarines with great success. After 1942, the USAAF began to assist in this anti-submarine campaign mainly using PBY's from Canada and Greenland.