Little is known of Major Charles Mackay at this time.

The British Genealogy site states the following:

Transferred from the Leinster Regiment to the R.F.C - Awarded the M.C., D.F.C, CdeG, and M.I.D. Wounded in 1916, survived the war and was granted a permanent commission in the RAF in 1919. source

Mackay, Charles Joseph (1895-1930). Born in Ireland. Commissioned as a Territorial officer in the Leinster Regiment, while student at Trinity College Dublin in 1913. Promoted to Lieutenant by the outbreak of war. Trained in Ireland until sent to France in Feb 1915. April 1915 wounded and sent home. While in hospital, transfer to the RFC came through. After training posted to No 2 Squadron in France Dec 1915. July 1916 transferred to No 4 Squadron. Dec 1916 posted to Home Establishment as Instructor in aerial photography and flying. Aug 1917 sent back to France as a Flight Commander in No 9 Squadron. Dec 1917 appointed OC No 59 Squadron, promoted to temporary Major. Later served in Ireland, at the Air Ministry in London, in Iraq and Egypt. Attended RAF Staff College, Imperial Defence College and finally was Instructor at RAF Staff College Andover, where died. source