Returning to Australia, De La Rue joined the short-lived Australian Air Corps in 1920, and became a founding member of the RAAF in March 1921.

[1] De La Rue transferred to the Royal Navy's Transport Service shortly after the outbreak of World War I, operating on troop ships between England and France.

Offered a permanent commission in the RAF that August, he nevertheless returned to Australia and sought employment through Lieutenant Colonel Stanley Goble, an ex-RNAS pilot then seconded to the Navy Office.

[3] On 17 June 1920, in an Airco DH.9A, De La Rue accompanied Captain Adrian Cole on a flight to an altitude of 27,000 feet (8,200 m), setting an Australian record that stood for more than ten years.

1 Course" at the Australian Army's Central Training Depot in Holsworthy, New South Wales; his fellow inductees included Flying Officers George Jones, Arthur Murphy, and Raymond Brownell.

[11] During the 1920s, De La Rue held a series of postings at RAAF Point Cook, Victoria, and at Air Force Headquarters, Melbourne.

[1] In May 1922, then in charge of the Seaplane Flight, he crashed an Avro 504L into Port Phillip; his rescuers claimed that his main concern following the mishap was the state of the corduroy trousers he was wearing.

[12] De La Rue married Clara Stone in a Presbyterian ceremony at Scots Church, Melbourne, on 1 October 1923; the couple would have a daughter.

[1] He had another escape in August 1925 when he crashed a Sopwith Pup into a hangar; a witness said that De La Rue, who was "renowned for his fiery Gallic temper", strode from the wreckage and began to violently abuse the aircraft.

Air Marshal Richard Williams, Goble's long-time rival for leadership of the Air Force in the 1920s and '30s, later contended that the CAS was unduly favouring his fellow RNAS veteran and seaplane specialist to lead what would have been the RAAF's largest formation to date, particularly considering that other contenders for the role such as Group Captains Cole, Frank McNamara, and Henry Wrigley had greater landplane experience than De La Rue.

[17] Sometime in the latter half of 1940, De La Rue was seeing dinner guests off the base at RAAF Richmond and attempted to re-enter the perimeter via the main gate.

[18] After completing his tenure at Richmond, De La Rue briefly took the role of senior air staff officer (SASO) at Central Area Command in October 1940.

[1] The following month, his name was put forward to establish an RAAF depot in London to look after the interests of the many thousands of Australian airmen disembarking there, but financial considerations led to the plan being scuppered temporarily.

[21][22] Meanwhile, De La Rue also missed out on a potential posting to the Middle East that was suggested by the British but turned down by the Australian government.

[28] Handing over Western Area Command to Air Commodore Ray Brownell in January 1943, De La Rue became Inspector of Administration at RAAF Headquarters, in which post he saw out the rest of the war.

In recommending early retirement, the CAS, Air Vice Marshal George Jones, noted that De La Rue possessed "fairly good Service knowledge" and was of strong character, but that "sometimes his efforts [were] ill-directed".

[1] On 31 March 1971, he was among a select group of surviving foundation members who attended a celebratory dinner at the Hotel Canberra to mark the RAAF's Golden Jubilee; his fellow guests included Air Marshal Sir Richard Williams, Air Vice Marshals Henry Wrigley and Bill Anderson, and Wing Commander Sir Lawrence Wackett.