With the outbreak of the First World War, Royal Flying Corps squadrons were deployed to France in August 1914. Although the configuration and effectiveness of the deployed forces owed much to Sykes, as a middle-ranking officer he lacked the seniority thought necessary for command in the field. General Henderson became the General Officer Commanding the Royal Flying Corps in the Field and Sykes acted as his Chief of Staff from 5 August 1914. On 22 November 1914, Henderson was appointed General Officer Commanding the 1st Infantry Division and Sykes took up command of the Royal Flying Corps in the Field. However, Sykes did not spend long in command. The decision to post Henderson and replace him with Sykes was not to Lord Kitchener's liking and he ordered a reversal of the posting. On 21 December 1914, Henderson resumed command of the Royal Flying Corps in the Field and Sykes was granted the temporary rank of colonel and once again made his chief of staff. He was promoted to the substantive rank of brevet lieutenant colonel on 18 February 1915. With the rapid expansion of the corps, there was a growing debate between those who believed that the corps should remain under central control and those who hoped that its units could be placed under the control of the corps or divisional commanders. Unsurprisingly as chief of staff, Sykes took the former view and following increasing arguments, Sykes was posted on 26 May 1915 being placed at the disposal of the Admiralty.