Branch folders accumulated by the Air Historical Branch and unregistered papers from British Forces in the Middle East relating to operations, intelligence etc., mainly in 1915 to 1922, and from the Sudan Defence Force 1920 to 1939. The bulk of the series, however, consists of unregistered papers, relating to the Second World War and the few years before and after it, received from many Air Ministry Branches and from the British Bombing Research Mission, the British Bombing Survey Unit, the Empire Air Navigation School, GHQ Home Forces and the RAF Staff College and various other commands and establishments in Britain and overseas. To these have been added more recent papers accumulated by the Branch, and covering a wide range of subjects. The series also includes sections of papers under the names of Air Chief Marshall Sir Robert Brooke-Popham, Sir Henry Tizard and Sir Harold Howitt, a member of the Air Council and Air Supply Board.
Included in this series are a large number of important papers collected for use in the official history of the department and which otherwise would have been in AIR 2, but which were kept separate by the Historical Branch of the Air Ministry and were placed in this series.