The Privateer was externally similar to the Liberator, but the fuselage was longer to accommodate a flight engineer's station, and it had a tall single vertical stabilizer rather than the B-24's twin tail configuration.

The single vertical tail was adopted from the USAAF's canceled B-24N design (and was slightly taller on the Privateer) because it would increase stability at low to medium altitudes for maritime patrol.

The Ford Motor Company, which produced B-24s for the United States Army Air Forces, had earlier built an experimental variant (B-24K) using a single tail.

The single tail design was used on the B-32 Dominator and PB4Y-2 and was slated for the US Army Air Forces' proposed B-24N production model to be built by Ford, but that order (for several thousand bombers) was canceled on 31 May 1945.

Electronic countermeasure (ECM), communication and radar antennas also protruded or were enclosed in fairings at various locations on the fuselage of the Privateer, including a manually retractable AN/APS-2 radome behind the nose wheel well.

Several PB4Y-2 squadrons saw operational service in the Pacific theater through August 1945 in the reconnaissance, search and rescue, electronic countermeasures, communication relay, and anti-shipping roles (the latter with the "Bat" radar-guided bomb).

[4] The French Aéronavale was supplied with Privateers via the Mutual Defense Assistance Act, which they used as bombers during the Indochina War and later operated out of Bizerte, Tunisia and Algiers.

They were then redesignated QP-4B under the 1962 United States Tri-Service aircraft designation system, becoming part of the new patrol number series between the Lockheed P-3 Orion and the Martin P-5 Marlin.

On 18 July 2002, one such refitted P4Y, BuNo 66260 (seen in picture to right) operated by Hawkins and Powers Aviation of Greybull, Wyoming broke up in flight while fighting a wildfire near Rocky Mountain National Park.

[7] Despite the fact that the crash was the result of poor maintenance, and a much newer C-130 based aircraft also broke apart due to similar stresses, all remaining Privateers were retired.