In the aftermath of the Japanese attack on Pearl Harbor, a number of aircraft that had been allocated to the RAF under Lend Lease were instead taken over by the USAAC. This happened to 75 Liberator IIs, which were operated by the USAAF as the LB-30. Like the Liberator II they featured the longer nose that would become standard on all later Liberators, The .303in guns used by the RAF were replaced by the .50in guns standard in American service. A twin gun Martin powered turret was placed in the dorsal position, in place of the four-gun Boulton-Paul turret used on the Liberator II. The powered tail turret used on the British aircraft was replaced by a manually operated twin gun position.
The LB-30 was used by a number of units as both bomber and transport aircraft. Amongst those units was the 6th Bombardment Group, which used the LB-30 in the Panama Canal Zone, the 7th Bombardment Group, which flew one large group of LB-30s to India, the 19th Bombardment Group, which used them during the desperate fighting in Java, and the 29th Bombardment Group, which used them over the Aleutian Islands from bases in Alaska. Twenty three of the aircraft were eventually returned to the RAF.