The second wave, making up of 54 land-based aircraft (27 Mitsubishi G3M medium bombers and 27 Mitsubishi G4M medium bombers) arrived over Darwin just before midday. The town's air raid sirens were sounded at 11:58 am when the bombers were sighted. The Japanese force separated into two groups flying at 18,000 feet (5,500 m). One of these formations attacked RAAF Base Darwin from the south-west while the other approached from the north-east. The two formations arrived over the base at the same time, and dropped their bombs simultaneously. The Japanese bombers then turned, and made a second attack on the base. Due to defective fuses, the Australian heavy anti-aircraft flak gunners were unable to damage any of the high-flying Japanese aircraft.  The bombers left the Darwin area at about 12:20 pm.