In August 1914, when the
First World War broke out, Casey was working for the
P&O. and on 30 May he was posted to for duty with the
Royal Naval Air Service. On 27 May 1916 Casey's Royal Naval Reserve commission was cancelled, and the following day he was re-commissioned as a probationary flight sub-lieutenant in the Royal Naval Air Service. On 3 August 1916 he was confirmed in his rank of flight sub-lieutenant, with seniority from 28 May. Casey served in No. 2 Wing, and was eventually posted to
No. 3 (Naval) Squadron to fly the
Sopwith Pup single-seat fighter. He gained his first aerial victory on 17 March 1917, driving down out of control a
Halberstadt D.II fighter over
Bapaume. and gained his second victory a week later, driving down an
Albatros D.III fighter on 8 April. He then gained seven more victories, six of them D.III fighters, in only twelve days, from 21 April to 2 May. and on 22 June was awarded the
Distinguished Service Cross. His citation read: Appointed to the
acting rank of flight commander, Casey died in a flying accident during a test flight on 11 August 1917. He is buried in
Adinkerke Military Cemetery in
De Panne,
West Flanders, Belgium. ==List of aerial victories==