The Short Empire was not designed for combat. Built by Short Brothers in the mid-1930s, the S.23 was among the most elegant airliners of its era - a four-engined monoplane flying boat that carried seventeen passengers in something approaching luxury across the routes of the British Empire, from Southampton to Singapore to Sydney. Powered by four Bristol Pegasus radial engines, the Empire could make 200 miles per hour at full throttle and had a range of roughly 760 miles. Corio, named after the town of Corio in Victoria, entered service with Qantas in October 1938, was sold to Imperial Airways in September 1939, and then leased back to Qantas under its new British registration, G-AEUH. By January 1942, with the Japanese advancing rapidly through Southeast Asia, Corio was no longer carrying mail and tourists. It was flying into war zones to bring people out.

Koch left Darwin at dawn on 30 January 1942, heading for Kupang on West Timor. From there, Corio would continue to Surabaya on Java, where refugees fleeing the Japanese invasion were desperate for transport to Australia. The flying boat carried eighteen people - crew and passengers - on what amounted to an evacuation run. The Pacific War was barely seven weeks old. Japan had struck Pearl Harbor on 7 December, invaded Malaya and the Philippines, and was now sweeping through the Dutch East Indies. The route Koch was flying crossed some of the most contested waters on Earth. Kupang itself would fall to Japanese paratroopers in less than three weeks.

Thirteen nautical miles from the West Timor coast, flying at just 400 feet above the water, Corio was jumped by seven Mitsubishi A6M Zero fighters. The Zero was the finest carrier-based fighter in the Pacific in early 1942 - fast, agile, and lethal against anything it caught in the open. Against an unarmed flying boat lumbering along at low altitude, it was no contest. Koch did the only thing he could. He pushed the throttles to the stops, dove toward the surface, and began zigzagging at maximum speed, so low that the Empire's wing floats bounced off the sea. The Zeros made repeated passes, their cannon and machine-gun fire perforating the fuselage and killing passengers in their seats. When two engines caught fire and power failed, Corio hit the water nose-first at high speed roughly three nautical miles from the mouth of the Noelmini River. The impact broke the fuselage in half.

Of the eighteen people aboard, thirteen died - some killed by the strafing, others in the crash itself. Koch, wounded in an arm and a leg, was thrown clear of the wreckage by the force of the impact. He found himself in the sea, bleeding, with the shattered remains of Corio sinking around him. It took him three hours to swim to shore. Four other survivors also made it, and the group was eventually rescued by a Dornier Do 24 flying boat of the Royal Netherlands Navy. Koch was evacuated to Darwin Hospital to recover from his wounds. He had been there less than three weeks when, on 19 February 1942, Japanese bombers struck Darwin in two devastating raids - the first foreign attack on Australian soil. Koch survived that too, though the hospital shook around him.

A lesser pilot might have found a desk job. Koch went back to flying. On 22 April 1943, he was at the controls of Camilla, another Qantas Short Empire, on a flight from Australia to New Guinea. Bad weather closed in around Port Moresby, and with fuel running critically low, Koch was forced to ditch the flying boat in the open sea. He survived again. After the war, Koch's reputation for skill under impossible conditions followed him into peacetime aviation. He was recruited by Lester Brain to join Trans Australia Airlines at its founding, specifically hired as Senior Pilot on the DC-4 Skymaster. The waters off West Timor where Corio went down remain unmarked - no memorial, no wreckage visible from the surface. The Timor Sea keeps its dead quietly. But Koch's story endures as one of the most remarkable survival accounts in early Qantas history, a reminder that the age of flying boats was as dangerous as it was romantic.