Consolidated Aircraft won the original contract from the US Army Air Corps in 1939 to build a bomber that could exceed the performance of the B-17. Their prototype, the XB-24 first flew in December 1939. Slightly smaller than the Flying Fortress, it had four 1,200-hp Pratt & Whitney R-1830-65 Twin Wasp turbocharged radial piston engines which enabled it to fly farther with a bigger bomb load than the B-17.

Of seven service-test YB-24s, six were sent to the Royal Air Force (RAF) in 1940 under the export designation LB-30A. Because they lacked turbosuperchargers and self-sealing fuel tanks, the RAF found them unsuitable for combat duty over Europe. Instead, they were stripped of their armament and put into service as transports on the Trans-Atlantic Return Ferry Service, which had been established to send air crews to Montreal to take delivery of American aircraft consigned to the British war effort.

Flying for the Army Air Corps as the B-24 and the U.S. Navy as the PB4Y-1, the plane also saw service in the Royal Air Force where it was known simply as the Liberator. There was also a transport version known as the C-87, one of which was Winston Churchill's personal aircraft, carrying him to historic meetings at Moscow and Casablanca, among other locations. Before the last one was retired from Air Force service in 1953, the plane was produced in variations ranging through type M. The various model numbers were often the result of minor changes, like the relocation of internal equipment, but one major revision, the conversion of the standard Navy B-24 (PB4Y-1) to the PB4Y-2 Privateer, involved a significant rework that exchanged the familiar twin tail for a single tall tail fin and rudder combination. It also had a stretched forward fuselage that placed the pilot's compartment well in front of the un-turbocharged Pratt & Whitney R1830-94 Twin Wasp engines.

One of the features that distinguished the B-24 from the B-17 were its tricycle landing gear, the first installed in a heavy operational aircraft. Other features were the mid-mounted, high-lift Davis wing that achieved 20 percent less drag than conventional airfoils of the time, twin tail fins, oval-shaped engine cowlings necessitated by the mounting of turbosuperchargers, unique roll-up bomb bay doors that reduced drag considerably when open and a fully retractable ventral machine gun turret. The B-24 was also the first to employ Hamilton hydromatic quick-feathering three-blade propellers.

With an empty weight of 36,500 lbs (an empty B-29 was almost double that weight), the B-24H/J could takeoff with 71,200 lbs (full fuel load and 12,800 lbs of bombs). Its length was 67 ft, wing span 110 ft and height stood at 18 ft. At 25,000 ft its cruising speed was 215 mph, top speed was 290 mph. It had 10 12.7 mm (50 calibre) machine guns in nose, upper/ventral ball turrets and tail turret and lateral positions.

While designed as a heavy bomber, the B-24 experienced more than 100 modifications and conversions for such assignments as photography, mine laying and cargo hauling (including a C-109 fuel tanker version that flew "the Hump" to refuel B-29s operating out of forward bases in China). More than 18,000 B-24s were built during WWII, more than any other American aircraft. Given its abilities and "convert-abilities", the numbers make perfect sense. However, a post war attempt to combine portions of the B-24 and PB4Y-2 with a new fuselage to create the Convair Model 39 airliner was not a commercial success, with only one prototype being built.

Of the many thousands of B-24s and derivatives built, only three remain airworthy (Two B-24Js and one LB-30), all in the United States.

The B-24 flew with a crew of 10 and numerous famous personalities flew in them. Jimmy Stewart was a B-24 pilot, as was Joe Kennedy whose PB4Y exploded in flight over England. Others who served as B-24/PB4Y pilots were Tyrone Power, Lloyd M. Bentsen, George McGovern and Robert Altman, the producer/director. Walter Matthau was a radioman/gunner and served under Jimmy Stewart. Robert Stack was a B-24 gunnery instructor.

Michael Russell Your Independent guide to Aviation