 Promoted Brevet Lieutenant-Colonel on 29 November 1915, he went back to the War Office as assistant director of military aeronautics.In 1916, he was appointed director of aircraft equipment, in charge of design, supply, and maintenance, and subsequently made a temporary brigadier-general.Faced with extraordinary demands for more and better aircraft, an overwhelmed system of procurement, and malicious attacks from superiors, an overworked MacInnes suffered a breakdown in the fall of 1916 and he left the directorate in early 1917.