At Cape Gloucester, the 1st Marine Division had an air force of its own consisting of Piper L-4 Cubs and Stinson L-5s provided by the Army. The improvised air force traced its origins to the summer of 1943, before the division plunged into the green inferno of New Britain. Lieutenant Colonel Kenneth H. Weir, the division's air officer, and Captain Theodore A. Petras, the personal pilot of Major General Alexander A. Vandegrift, then the division commander, concocted a plan for acquiring light aircraft mainly for artillery spotting. The assistant division commander at that time, Brigadier General Rupertus, had seen Army troops making use of Piper Cubs on maneuvers, and he promptly presented the plan to General MacArthur, the theater commander, who promised to give the division twelve light airplanes in time for the next operation.

When the 1st Marine Division arrived at Goodenough Island, off the southwestern tip of New Guinea, to begin preparing for further combat, Rupertus, now a major general and Vandegrift's successor as division commander, directed Petras and another pilot, First Lieutenant R. F. Murphy, to organize an aviation unit from among the Marines of the division. A call went out for volunteers with aviation experience; some sixty candidates stepped forward, and 12 qualified as pilots in the new Air Liaison Unit. The dozen Piper Cubs arrived as promised; six proved to be in excellent condition, three needed repair, and another three were fit only for cannibalization to provide parts to keep the others flying. The nine flyable planes practiced a variety of tasks during two months of training at Goodenough Island. The airmen acquired experience in artillery spotting, radio communications, and snagging messages, hung in a container trailing a pennant to help the pilot see it, from a line strung between two poles.

The division's air force landed at Cape Gloucester from LSTs on D-Day, reassembled their aircraft, and commenced operating. The radios installed in the L-4s proved too balky for artillery spotting, so the group concentrated on courier flights, visual and photographic reconnaissance, and delivering small amounts of cargo. As a light transport, a Piper Cub could drop a case of dry rations, for example, with pinpoint accuracy from an altitude of 200 feet. Occasionally, the light planes became attack aircraft when pilots or observers tossed hand grenades into Japanese positions.

Before the Marines pulled out of New Britain, two Army pilots, flying Stinson L-5s, faster and more powerful than the L-4s, joined the division's air arm. One airplane of each type was damaged beyond repair in crashes, but the pilots and passengers survived. All the Marine volunteers received the Air Medal for their contribution, but a specially trained squadron arrived from the United States and replaced them prior to the next operation, the assault on Peleliu.