No. 1 Flying Boat Maintenance Unit RAAF (1 FBMU) was established at the RAAF Bowen Flying Boat Base in north Queensland on 10 October 1943 using personnel posted from No. 22 Operational Base Unit. Squadron Leader O'Donnell, their first Commanding Officer arrived on 4 November 1943. Catalinas, Martin Mariners, Seagulls and other Flying Boats were reconditioned and serviced by 1 FBMU during WWII.

There were initially 12 Officers and 284 airmen in 1 FBMU along with the following Catalinas:-

• A24-49
• A24-54
• A24-57
• A24-64
• A24-65

Squadron Leader E. F. Easterbrook took over as Commanding Officer on 2 June 1944.

The Minister for Air and his party inspected the Unit on 16 June 1944 and carried out an investigation into hiring of Barracks for the Bowen Flying Boat Base.

On the 19 September 1944, a United States Army Air Force Catalina was alloted to the Unit for repairs. It had seriously damaged its planing surfaces and landed on a nearby airfield. The mainplane outer panels were removed and transported from the other airfield to the slipway at the Flying Boat Base. The aircraft was transported by road to the Flying Boat Base after negotiating some railway crossings and the main streets of Bowen.

A private launch in trouble off Bowen was brought in to the Flying Boat Base by one of the Unit's marine craft on 12 October 1944. On 19 December 1944, Catalina A24-101 attached to the Unit carried out a search for a Norseman aircraft which had made an emergency landing en route from Rockhampton to Mackay. The Norseman was located by another aircraft.

Squadron Leader G. L. Grendon took over as Commanding Officer on 14 December 1944.

On 21 December 1944, the Unit carried out a search for HMAS Leilani, an unarmed Naval Auxiliary Patrol Harbour Defence Craft, which had been damaged in a collision en route from Rockhampton to Townsville. HMAS Leilani managed to make it into Port Denison under its own power.

On 2 January 1945, Unit Headquarters moved from Herbert Street to the new Administration building in the slipway area.

Catalina A24-92 was damaged when landing at the Bowen Flying Boat Base on 19 January 1945 on a Ferry Flight from 2 Flying Boat Repair Depot at Rathmines to 111 Air Sea Rescue Flight. Flight Lieutenant Cox of 20 Squadron RAAF had his left forearm severed by a propeller.

Squadron Leader E. J. Stocker took over as Commanding Officer on 2 February 1945.

1 FBMU's Fire Tender assisted in confining a fire in a civilian garage on 17 May 1945.

On 6 August 1945, Mariner Flying Boat A70-7 arrived at the Flying Boat Base to establish the Air-Sea Rescue base at Bowen for 114 Air-Sea Rescue Flight.

1 FBMU started to vacate the many civilian properties that had been requisitioned in Bowen on 2 September 1945. The first contingent of WAAAFs left the Unit for Townsville on 30 October 1945. The remainder of the WAAAFs left the Unit later that week. As the WAAAFs had used the Hotel Denison for their Barracks in recent times, the hotel was returned to its owner on 13 November 1945.

Flying Officer R. C. Henzell took over as Commanding Officer on 25 February 1946.