Numerous false sightings of mysterious aeroplanes, thought to be German and hostile, were reported by ordinary people around Australia in the Autumn of 1918. These reports were investigated by defence authorities, who initiated a maximum effort to find the merchant raiders presumed to be the source of the aeroplanes. The scare is interpreted in the context of reports that a German seaplane had flown over Sydney in 1917; fears that the German offensive in France would lead to an Allied defeat; wartime paranoia about German subversion; and the growth of negative airmindedness thanks to the wartime press.