During mid-1944, the Army determined that Convair/San Diego and Ford/Willow Run would be capable of meeting all future requirements for Liberator production, and ordered that production of the Liberator at Convair/Fort Worth, Douglas/Tulsa and North American/Dallas be terminated. Production of the Liberator ended at Douglas in July of 1944, but Convair/Fort Worth and North American/Dallas continued B-24J production until the end of 1944, mainly filling Lend-Lease contracts for Britain.
The B-24L was the first product of the new, downsized Liberator Production Pool. It was an attempt to reverse the trend toward ever-increasing weight of the Liberator as more and more armament, equipment, and armor had been added, with no corresponding increase in engine power.
The overweight problem with the B-24J had gotten so bad that field commanders in the Pacific had ordered that the Sperry ventral ball turret be removed and replaced by a pair of hand-held 0.50-inch machine guns firing through a floor hatch. The increased availability of long-range escort fighters in late 1944 in the northern European theater made this option possible there as well. The B-24L made the deletion of the ventral ball turret standard. This turret was replaced by a manually-operated twin 0.50-inch machine gun installation fitted to a ring mount and firing through a ventral hatch behind the bomb bay.
The B-24L also introduced the new Convair M-6 "Stinger" tail turret, which was originally designed by the Consolidated Vultee Modification Center at Tucson, Arizona. It had a distinctive blown glazing which had no framing. The M-6 turret was manually operated and offered a savings of 200 pounds in weight over the Consolidated A-6B turret. In addition, it had a wider field of fire.
The Emerson A-15 cylindrical-geometry nose turret was installed, and the tall Martin A-3D dorsal turret was standard equipment. The B-24L used the larger rectangular-shaped navigator windows that had been introduced at the end of the B-24J production block. With the B-24L, the K5 gun mounts and enclosed waist gun positions finally became standard equipment on Convair/San Diego-built Liberators.
The weight reduction program resulted in the loss of over 1000 pounds of weight, which resulted in improved performance and better handling.
Larger bombardier scanning windows were introduced at Block 5, as well as an aileron tab on the port wing. Wingtip static dischargers were added at Block 15.
The first Convair/San Diego-built B-24L was delivered to the USAAF on July 1944, with the first Ford-built B-24L being delivered one month later. A total of 417 B-24Ls were built by Convair/San Diego, with 1250 being built by Ford/Willow Run.
On July 10, 1944, the USAAF ordered that Convair/San Diego and Ford/Willow Run deliver B-24Ls without any tail armament fitted. This allowed the aircraft be fitted at one of the Army's modification centers with tail armament appropriate for the theatre in which they were to be serving. At first, the planes delivered without tail armament by Convair/San Diego continued to be designated B-24L, whereas those built by Ford/Willow Run were designated B-24M. However, these designations were only used for a short time, with the Army later redesignating the 115 Ford/Willow Run-built B-24Ms to B-24Ls. Some of the "theatre" tail armament fitted to the B-24L included 41 planes fitted with the M-6A "Stinger" tail turret, 190 planes fitted with Consolidated A-6B tail turrets, and 186 planes fitted with a hand-held twin 0.50-inch machine gun in an open tail position.
In order to meet requirements for the training of B-29 crews, several B-24Ls were converted with square-cut nose windows and were equipped with chin, ventral, dorsal, and tail turrets. These planes were later redesignated TB-24L. This designation was also applied to B-24Ls converted into trainers for radar operators.
Numerous B-24Ls were converted into C-109 tankers for use in carrying aviation gasoline across the Hump in support of B-29 operations in China. At one time, it was proposed to acquire as many as 2000 C-109 tankers, but the B-29 operations were transferred from China to the Marianas where they could better be supported by seaborne tankers, and this plan was scaled way back. The C-109s were then transferred to the Air Transport Command.
Numerous B-24Ls were supplied under Lend-Lease to Britain as Liberator VI and VIII.
Two B-24Ls are known to survive. An ex-Indian Air Force B-24L (USAAF serial 44-51054, IAF serial number HE773) is on display at the National Aeronautical Collection in Trenton, Ontario in Canada. An ex-RAF B-24L (KN751) is on display at RAF Cosford near Wolverhampton in England.
44-41390/41448 Consolidated B-24L-1-CO Liberator 44-41449/41548 Consolidated B-24L-5-CO Liberator 44-41549/41648 Consolidated B-24L-10-CO Liberator 44-41649/41748 Consolidated B-24L-15-CO Liberator 44-41749/41806 Consolidated B-24L-20-CO Liberator 44-49002/49251 Ford B-24L-1-FO Liberator 44-49252/49501 Ford B-24L-5-FO Liberator 44-49502/49751 Ford B-24L-10-FO Liberator 44-49752/50001 Ford B-24L-15-FO Liberator 44-50002/50251 Ford B-24L-20-FO Liberator