In 1911 Captain Sykes was a Cavalry Officer in the Kings Hussars and a GSO at the War Office. He learned to fly at Brooklands in 1911 and obtained Pilots Certificate No. 95. He already had a ballooning certificate in 1904. After learning to fly he attended a Military Aviation meeting at Rheims and he appears to have had a long sighted view of aviation.
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In April 1912 a Royal Warrant proclaimed the formation of the Royal Flying Corps with a Military Wing at Farnborough and a Naval Wing at Eastchurch. The first Commandant of the Military Wing was Major Sykes, a post he held until 1914. In June 1915 the Air Department of the Admiralty decided to investigate the general situation with the RNAS in the Eastern Mediterranean and Sykes was sent out to size up the situation. This was not very popular with Commander Samson but Sykes report was accepted. He recommended that a second squadron should be sent out and that there should be a R.N.AS. Headquarters with an officer in charge of all operations. The freebooting days were coming to an end and Sykes was commissioned into the Royal Marines as a Colonel. (Temporary Wing Capt. RNAS), to take overall command which he did until the end of the Gallipoli campaign in March 1916.

On return to England. Sykes was appointed to another War Office job and relinquished his RM commission.
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In 1918 Sykes reappeared in aviation when the Royal Air Force was formed on 1st April. At that time he was a Brigadier General on the General Staff, Supreme War Council, Versailles. Previously Trenchard had agreed to become Chief of the Air Staff under Lord Rothermere but the friction between the two became so great that on 19 March 1918 he resigned before officially taking up the job on 1st April. Instead he took command of the Independent Bomber Force in France on 8 May 18. His place was taken by F.H. Sykes on 13 April 18 who became the first Chief of the Air Staff to occupy the chair, since Trenchard had already resigned before the RAF came into being on 1st April.
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It cannot be claimed that Sykes was a serving Royal Marine at the time of his appointment but he had served with distinction as a Colonel in the Dardanelles Campaign when he was Commander of the RN.AS. units operating in the area. The copy of the entry in his Statement of Service used as a frontispiece to these papers gives an indication of his ability, and the experience he gained whilst in RM Uniform must have contributed very largely towards his selection for the appointment. One can therefore, quite reasonably claim that the first Chief of the Air Staff was formerly a Royal Marine Officer.
A political move followed on 15 February 1919 when he was relieved by Trenchard and Sykes then took over as the first Controller General of Civil Aviation which he held from 1919 to 1922.
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He was Governor of Bombay from 1928 to 1933 and later served as a Member of Parliament.
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He died on 30th September 1954.