In March 1940, Fadden was named a minister without portfolio in the government of Robert Menzies, who led the United Australia Party in a coalition with the Country Party. A few months later, following the deaths of three senior ministers in an air crash, he took over as Minister for Air and Minister for Civil Aviation. In October 1940, Fadden replaced Harold Thorby as deputy leader of the Country Party. The leadership was vacant at the time, following Archie Cameron's resignation, so Fadden became acting leader of the party and "de facto" deputy prime minister. Menzies subsequently promoted him to Treasurer of Australia.