As copilot of a PBY-5, he departed for a patrol south of Amboina, Moluccas on 19 February. With Lt. Thomas H. Moorer as pilot, the patrol plane spotted a merchant ship off Melville Island, Australia, and turned to investigate. About 09:20, nine Japanese fighters, part of a 70 plane force en route to bomb Darwin, Australia, jumped the PBY. Soon the plane was in flames, its port engine out and fuel streaming along the fuselage. Despite the attacking fighters, Moorer and Mosley landed the plane. In Moorer's words, Mosley assisted by handling the throttle "although dazed and bleeding profusely from a wound in the head." SS Florence D., an American merchant ship carrying ammunition to the Philippines, rescued the crew. Later that day, Japanese carrier planes attacked the unarmed ship with 500 pound bombs. Survivors, including Mosley, made Bathurst Island in two lifeboats about midnight and an RAAF patrol plane spotted them on the 21st. The next morning, HMAS Warrnambool (J202), an Australian subchaser, rescued them and carried them to Darwin on 23 February.