Miller then transferred to the
Royal Flying Corps, and was granted a commission as a second lieutenant (honorary lieutenant) on 15 May 1918, to serve as an
observer officer. Miller was posted to
No. 18 Squadron RAF on 4 April, only days after the Royal Flying Corps and the
Royal Naval Air Service were merged to form the
Royal Air Force (RAF), to fly in the
Airco DH.4 two-seater day bomber. He gained his first aerial victories while flying with Captain
David A. Stewart, accounting for two
Fokker D.VII on 30 May 1918. From then on he flew with Captain
George Darvill, shooting down four more D.VIIs, one each on 8 and 28 July, and two on 4 September. Miller was
wounded in action on 6 September 1918. On 12 June 1919 Miller was transferred to the RAF's Administrative Branch, and then to the unemployed list on 10 October. He relinquished his commission in the Northumberland Fusiliers "on account of ill-health caused by wounds" on 2 November, retaining the rank of lieutenant, but did not relinquish his RAF commission until 30 June 1921, after accepting an appointment in the
Territorial Force. ==Post-war and later life==