Royal Navy engineers landed in August 1941 from HMS "Guardian" to clear and construct airstrips on Gan for the Fleet Air Arm. In the interim, Catalina and Sunderland flying boats operated from jetties on the northern, sheltered side of Gan. Large oil tanks were built on Gan, and on Hitaddu Island on the western edge of the atoll; vital elements for a naval base. These were visible from a long distances at sea, but this was unavoidable, given the atoll's low profile.