Nicknamed 'Lumbering Lib' the B-24 was one of the most produced aircraft during the Second World War, with a total of over 18,000 manufactured. The Consolidated B-24 Liberator would serve with the Allied forces in all theatres of war and would help close the Mid-Atlantic gap.

The B-24 Liberator came to life during 1939, when in January of that year the United States Army Air Corps asked Consolidated to produce a design study of a heavy bomber whose range, speed and service ceiling in particular as well as overall performance being an improvement on the B-17 Flying Fortress.

Consolidated named their design the Model 32 and it was the second plane to use the 'Davis wing', the flying boat the company was working on for commercial and later military use, the Model 31, was the first. With Consolidated speeding ahead with the heavy bomber project the USAAC were keen to keep the pace going and on the 30th March 1939, just two months after the design study began, a contract to build a prototype, known as the XB-24, was awarded, but this had to be produced by the end of the year. So with two days to spare, on the 29th December 1939 the prototype Liberator made its maiden flight. Powered by four 1,200-hp Pratt & Whitney R-1830-33 Twin Wasps engines and featuring tricycle landing gear, roller shutter style bomb-bay doors which could contain a bomb load of 8,000lb, nearly twice that of early B-17s.

Flight testing showed the aircraft to have potential and although a few changes were needed to meet the specification set out by the United States Army Air Corps, it was good news for Consolidated especially as a French purchasing mission had order 120 and the USAAC had ordered seven YB-24s for service testing and thirty six B-24As before the prototype flew. The YB-24s were delivered in 1940, but unlike the prototype, featured pneumatic de-icing boots on the leading edges of the wings, tailplane and fins.

Despite France being the first export order, when the first B-24s were ready France had surrendered to Germany so the Royal Air Force would receive the 120 ordered on top of the 164 ordered by the RAF already. The first one, re-designated LB-30A, flying on the 17th January 1941 with the initial batch of six being received by the RAF two months later in March. These six aircraft were unarmed and used as transport, firstly by British Overseas Airways Corporation and secondly by Ferry Command, to fly back pilots and crews who had delivered aircraft. A role the United States Army Air Corps would also use their B-24As for. The next delivery of planes occurred in June 1941 and saw the name Liberator given to the plane by the RAF and the Mk I saw service with Coastal Command. These planes included four 20mm cannons as additions to the five 0.30-in machine guns and the installation of ASV (Air-to-Surface Vessel) radar.

It was to be the Liberator II which was to be the first bomber version and as such had increased armament in the form of eight 0.303-in machine-guns, four a piece in Boulton Paul turrets, and had an increase in space to accommodate upto ten crew members. As with the Liberator I Coastal Command used the type and it was whilst with Nos 159 and 160 Squadron, who were based in the Middle East, during June 1942 that the type was first used in its intended role as a bomber, and although the Royal Air Force made use of this Mk the United States Army Air Corps did not.

A sole XB-24B prototype appeared featuring a number of changes and re-engined with turbocharged R-1830-41 engines. Other changes included dorsal and tail turrets with a pair of 0.50-in machine-guns in each. Nine of these aircraft were manufactured as the B-24C for the USAAC.

It was to be the next Mk, the B-24D, which became the first Liberator to be mass produced. Power would be supplied by four Pratt & Whitney R-1830-43 engines and as production progressed each batch of B-24Ds featured various changes over the previous batch produced. So it would be the B-24D that the United States Army Air Corps would use for the first time in the aircraft's intended role as a bomber and deliveries of the type to Squadrons based in the Middle East began in June 1942.

One of the earliest raids the B-24 undertook for the USAAC was on the 12th June when thirteen were dispatched, for what was to be considered an unsuccessful attack, to Ploiesti, Romania to attack the oilfields there. One hundred and seventy seven B-24s would take part the following year in the Ploiesti raid on the 1st August 1943 but suffered very heavy losses with 29%, fifty three, B-24s lost. 1943 also saw Very Long Range (VLR) Liberators start to enter service and along with escort carriers helped to close the Mid-Atlantic gap which had previously suffered from no air cover leading to increased shipping losses in this area due to U-boat activity.

The B-24E was next to be produced and featured minor changes and new propellers, whilst some had R-1830-55 engines installed. These were followed by the B-24G which had the fuselage nose lengthened by 10 inches and a gun turret installed in the upper nose, except for the first twenty five produced and these were exclusively built by North American Aircraft with a B-24H designation given to similar B-24s built by other manufacturers.

The next Liberator version to follow was the B-24J and this differed very little from the B-24H, with the major change being the design of the B-24D being re-engineered so it could have the A.6 tail turret modified to fit in the nose. The re-design was required due to the Emerson nose turrets being in short supply, although not all B-24Js were modified in this way. A B-24D would provide the basis for the XB-24K which had its own twin tail replaced with the single tail from a Douglas N-23 Dragon. This improved both the handling and stability of the aircraft.

The B-24L and M were to become the final production variants featuring differences in the tail turrets over their predecessors. The planned B-24N was to feature the single tail as tested on the XB-24K and just over 5,000 were ordered but with the Second World War coming to an end only the prototype, designation XB-24N, and seven YB-24N test aircraft were built by the time production ended on the 31st May 1945.

The United States Navy also used the type under the designation PB4Y-1 Liberator which lead to a fully navalised version coming to life known as the Consolidated PB4Y-2 Privateer. A special fuel tanker version of the type was also produced, known as the C-109, to deliver aviation fuel for B-29 Superfortresses operating in China. The B-24 was also used by the Royal Australian Air Force and Royal Canadian Air Force. Captured B-24s were also used by Kampfgeschwader 200 (KG 200), the special operations unit of the Luftwaffe. British Prime Minster Winston Churchill would also use a B-24 (AL505) named 'Commando' as transport.

With over 18,475 Liberators rolling of the production line the aircraft would be found in all theatres of war up until the end of World War 2 and post-war the B-24 was used in the Berlin Airlift (1948 – 1949).