He initially served in the Royal Naval Air Service during the First World War, where he became known as one of "the Zeppelin killers from Canada", after shooting down two airships.

[3][5] However, he had completed only three hours of training[3] in the Curtiss Model F flying boat at Hanlan's Point, when the school was forced to close for the winter.

On 10 May 1916, having accumulated 33 hours and 3 minutes flying time, he was granted Royal Aero Club Aviator's Certificate No.

[3] He was confirmed in his rank of flight sub-lieutenant in June,[7] and in August was posted to RNAS Great Yarmouth to fly patrols over the North Sea.

The Curtiss increased speed and gained height, and Leckie took over the controls as Galpin manned the twin Lewis guns mounted in the bow.

The aircraft dived down alongside and Galpin fired an entire drum of incendiary bullets at a range of about 50 yards.

Finally, at dawn on 8 September, as search operations were about to be called off, one of the pigeons was found, dead from exhaustion, by the coastguard station at Walcot, and shortly after midday they were rescued by the torpedo gunboat HMS Halcyon.

[2] While on patrol on 20 February 1918, Leckie spotted an enemy submarine on the surface, and attacked it with bombs, seeing one strike the vessel as it dived, leaving a large oil slick.

[15] On 4 June 1918 Leckie led an offensive patrol of four Felixstowe F.2A flying boats and a Curtiss H.12 towards the Haaks Light Vessel off the Dutch coast.

Despite further mechanical difficulties – two other F2A's also had problems with their fuel pipes and had to effect makeshift repairs while in the middle of the action – two German aircraft were shot down, and four badly damaged before the Germans broke off the action, for the loss of one F.2A and the Curtiss (its crew survived to be interned by the Dutch),[16] and one man killed.

[17] Leckie's force returned to Great Yarmouth, and in his report he bitterly remarked "...these operations were robbed of complete success entirely through faulty petrol pipes...

Responding to the report Major Egbert Cadbury jumped into the pilot's seat of the only aircraft available, a DH.4, while Leckie occupied the observer/gunner's position.

[3] Cadbury and Leckie, and another pilot Lieutenant Ralph Edmund Keys, then attacked and damaged another Zeppelin, which promptly turned tail and headed for home.

Zeppelins often shadowed British naval ships, while carefully operating at higher altitudes than anti-aircraft guns or flying boats could achieve, and out of range of land based aircraft, so the Harwich Light Cruiser Force set out with a Sopwith Camel lashed to a decked lighter towed by the destroyer HMS Redoubt.

When Leckie's reconnaissance flight reported an approaching Zeppelin, the Redoubt steamed at full speed into the wind, allowing the Camel's pilot Lieutenant Culley to take off with only a five-yard run.

Culley climbed to 18,800 feet, approached the L 53 out of the sun, and attacked with his twin Lewis guns, setting the airship on fire.

[29] Leckie and Major Basil Hobbs flew from Halifax to Winnipeg between 7 and 10 October 1920,[30][31] before other pilots and aircraft took over, finally arriving in Vancouver on the 17th.

[34] On 25 September he was posted the RAF Depot (Inland Area) as a supernumerary officer,[35] in order to attend the Royal Navy Staff College.

[40] He returned to the depot at RAF Uxbridge on 11 May 1927,[41] and on 26 August was posted to Headquarters, Coastal Area, while he waited for HMS Courageous to be commissioned.

[44] Leckie returned to dry land on 5 September 1929, when he was appointed commander of RAF Bircham Newton, Norfolk.

[54] Leckie's tenure as Director of Training ended on 28 November 1938,[55] and on 2 December 1938 he was appointed Air Officer Commanding, RAF Mediterranean, based at Malta.

[2] On 6 April 1942 Leckie was placed on the RAF retired list on accepting a commission in the Royal Canadian Air Force.