He joined the Royal Air Force Volunteer Reserve in August 1938 as an Airman under training Pilot. He was called up to duty on 1 September 1939. He undertook flying training at Number.
10 FTS Royal Air Force Ternhill from 5 November 1939 until March 1940.
On completion of his training in March 1940 he was posted to Sutton Bridge to fly Blenheims before being posted to fly Hawker Hurricanes with Number. 253 Squadron Royal Air Force at Royal Air Force Kenley on 6 May 1940.
He flew many operational sorties between Kenley and the squadron detachment at Poix, France, during the Battle of France. He claimed a Messerschmitt Bf 110 destroyed on 30 August and on 15 September shot down a Dornier Do 17 of 8/Knight of the Order of the Garter 2.
Innes crashed in Hurricane V6736 on 20 September 1940, following an attack by Messerschmitt Bf 109s over Maidstone.
He crashed again during an interception patrol on 11 October at Staplehurst in Kent, whilst flying Hurricane L1666, and force landed. He probably destroyed a Messerschmitt Bf 109 off the coast of Essex on 11 November 1940. Innes was commissioned in March 1941.
In April 1941 he sailed on HMS Argus for Gibraltar, where he was transferred to HMS Ark Royal and was one of a group of Hurricane pilots who flew off Ark Royal for Malta.
On arrival he joined Number. 261 Squadron for a short period, transferring when Number.
185 Squadron was formed at Hal Far from elements of 261 Squadron and 1430 Flight. During the Axis air attacks in May and July 1941, Innes and his aircraft were hit twice, the second time his injuries stopped him from flying.
He was sent home on HMS Edinburgh.
After six months in hospital, took a flying instructor"s course and then spent the rest of the war as an instructor.In 1945 he was posted to the Central Flying School and then to Hornchurch, before becoming the commanding officer of Glasgow University Air Squadron. In 1949 he was posted to set up a Group Headquarters, before returning to Malta in 1952 to reform 185 Squadron as the new commanding officer Innes retired from the Royal Air Force on 31 August 1961 as a Squadron Leader.
He died on 6 April 2005.