By far the most famous flying boat of World War II, the Consolidated PBY Catalina served in the air and naval forces of most Allied nations and saw action in every theater, one of its major accomplishments being the spotting of the Bismark at sea which led to its sinking. Among the missions of the 'Cat', as it was affectionally called, were long-range reconnaissance duties, anti-submarine patrols, and high-seas rescues as well as being a very effective fleet scout. The aircraft also had bombing capability and radar-equipped 'Black Cats' used torpedoes against Japanese shipping. One of the greatest attributes of the PBY was it's ability to stay on patrol for 24 hours at a time and thanks to this, substantial numbers of Catalinas served with RAF Coastal Command as well as the air forces of Australia, Brazil, Chile, Netherlands, New Zealand, Norway, South Africa, the USSR, and Canada (where they were also built) although the total number of foreign operators was approximately two dozen, most of them post-war. US Catalinas were not retired until 1957 although some remain in civil use mainly as aerial firefighters.

First flight of the prototye XP3Y-1 was on 28 March 1935 and initial PBY-1s entered service as early as 1936, more than 5 years before the US entered the war. Subsequent PBY-2 and PBY-3 variants differed only slightly until the PBY-4 appeared which featured an improved 1,050-hp engine and transparent fairings over gunner positions. It was meant to be the final production variant until the outbreak of war in Europe caused various nations to show interest, notably Britain, Canada, Australia and the Dutch, this led to the definitive PBY-5 with 1,200-hp engines and the prominent amid-ship blisters as well as the PBY-5A amphibian. Finally the PBY-6A amphibian had a search radar above the cockpit and taller vertical tail surfaces. Catalinas were also built by Boeing Canada as the PB2B-1/2 and by the Naval Aircraft Factory as the PBN-1 Nomad with a taller fin and modified nose.