On 25 November 1941 , following the loss of HMAS Sydney , one of No. 20 Squadron 's Catalinas was despatched to Western Australia to join a No. 11 Squadron Catalina in search @-@ and @-@ rescue missions , but they found only oil slicks . By the outbreak of war in the Pacific , No. 20 Squadron had a strength of six Catalinas and two Empire flying boats . Its personnel at the beginning of December numbered 14 officers and 118 men . The squadron undertook its first sortie of the Pacific War on 8 December ; a Catalina located three Japanese luggers in the vicinity of Thursday Island , Queensland . Later in the month it commenced anti @-@ submarine patrols and , in January 1942 , bombing raids against Japanese bases . As the Japanese advanced into the South West Pacific , No. 20 Squadron was also responsible for evacuating white civilians from areas threatened by invasion . On 21 January , one of its Catalinas located the Japanese fleet steaming for Rabaul and signalled a warning to the town 's Australian defenders before being shot down by anti @-@ aircraft fire ; it was the squadron 's first combat loss .