Cranwell. In April 1931, he transferred to the staff of the RAF College, until returning to Iraq in December 1933 as a member of the air staff, HQ Iraq Command. In January 1936, he returned to England, and attended the RAF Staff College at Andover. He was promoted to squadron leader on 1 April 1936 and to wing commander on 1 March 1939. Intelligence career In January 1937, he was appointed to the staff of the deputy directorate of Intelligence, and promoted to deputy director of intelligence (3) (DDI3) in 1940. In this role, he was head of the German branch of air intelligence. He was promoted to the rank of group captain in September 1941 and to (acting) air commodore in March 1942. In March 1942, he was promoted to director of intelligence (operations), reporting direct to the prime minister, Winston Churchill. Following the entry of the United States into the Second World War, Churchill sent Inglis to see President Roosevelt to persuade him to direct the United States war effort primarily against the German air force in Europe. Inglis stayed in the White House and held two meetings with Roosevelt, eventually persuading the president to go against his own advisors and agree to the British viewpoint, that the major American war effort must be directed towards the defeat of Germany first. According to Inglis's brother-in-law, Air Marshal Sir Victor Goddard,No other war decision by America was more significant for Europe and the World than that one. It is to be attributed to the clear trustworthiness of Frank Inglis that his vital, single-handed mission was successful, and it is to be attributed to his modesty that his part in that happening seems never to have come to the notice of historians. In October 1942, Inglis was promoted to Assistant Chief of the Air Staff (Intelligence), with the military rank of acting air vice marshal, succeeding Air Vice-Marshal Charles Medhurst, thus making him head of Air Intelligence. Later career At the end of the war, in August 1945, he was appointed Air Officer Commanding No. 23 Group, Flying Training Command (with Air Vice Marshal Sir Thomas Elmhirst succeeding him at RAF Intelligence). On 20 January 1947, he was appointed senior air staff officer, HQ Air Command Far East and on 20 October 1949 as senior air staff officer, HQ Flying Training Command. He reached the full rank of air vice-marshal