The Consolidated PB4Y Privateer was the result of the success of the Liberator bomber used for maritime patrol by the US Navy. Unmodified B-24 aircraft equipped with radar and Leigh light devices were used extensively for anti-submarine warfare and are largely credited for closing the Atlantic Gap thanks to their very-long range (VLR) capabilities. Nevertheless, it was decieded to develop a dedicated patrol bomber version which became the Privateer which was otherwise similar except for a stretched fuselage and a single large vertical fin which was also found on some later Liberator variants. They saw limited service in the Pacific at the end of the war (some equipped with underwing Bat glide bombs) but remained in service with the USN (as well as other nations such as France and Taiwan) post-war. They included improvements such as ASW radar while others were used for covert operations around the Soviet Union and with the US Coast Guard for air-sea rescue.

Modified versions of the B-24 were converted to maritime patrol bombers known as the PB4Y-1. A dedicated version was first flown on 20 September 1943 as the XPB4Y-2 converted from B-24D airframes. They entered service the following year as the PB4Y-2 Privateer and included the PB4Y-2B equipped with glide bombs as the only main wartime variant. They were renamed P4Y in 1951 with post-war models including the P4Y-2S with ASW radar and the P4Y-2G rescue aircraft for the USCG.