Commencing his service in the Australian Flying Corps (AFC) as a mechanic during World War I, he rose to become the RAAF's chief logistics officer for more than twenty years.

Commencing his working life as a coach and motor-body builder, he enlisted in the Australian Military Forces on 17 August 1914, soon after the outbreak of World War I.

[1][2] His experience in the motor industry led to assignment as an air mechanic with the Aviation Instructional Staff at Central Flying School (CFS), Point Cook.

30 Squadron Royal Flying Corps (originally the Mesopotamian Half Flight AFC), which moved into the city of Kut after its capture by British Empire troops in the Battle of Es Sinn.

The unit took part in the Battle of Ctesiphon in November, and organised supply drops to the British and Indian garrison in Kut during the siege that lasted from December 1915 until the following April.

[13] Mackinolty remained in England following the end of hostilities, serving as "officer in charge of Australian packing" at RAF Hendon, near London, from December 1919 to September 1920.

In this role he was responsible for crating and shipping to Point Cook the 128 aircraft and associated spares, weaponry, vehicles, hangars and other equipment that made up Britain's post-war Imperial Gift of Royal Air Force surplus to Australia, which eventually filled 19,000 cases.

[1][16] Promoted flight lieutenant, he was appointed Director of Transport and Equipment at RAAF Headquarters in 1929, effectively making him the Air Force's senior supply officer, a role he would occupy for the next twenty-two years.

[2] His continuous tenure in essentially the one post was comparable to the RAAF's other chief logistician, Squadron Leader (later Air Vice-Marshal) Ellis Wackett, who served as its senior engineer for twenty-four years, from 1935 to 1959.

[2][19] At around this time, he collaborated with Squadron Leader George Jones, then Director of Training, on an investigation into the state of aircraft production in Australia to highlight shortfalls in local defence in the face of possible future conflict with Japan.

[20] Raised to squadron leader, Mackinolty was appointed an Officer of the Order of the British Empire in the Coronation Honours on 11 May 1937, in recognition of his achievements in stores and accounting.

[26] Serving as AMSE for the remainder of the war, Mackinolty was credited with successfully managing the supply requirements of personnel and aircraft for an organisation that by 1945 had grown by a factor of fifty from its pre-war size, to become the world's fourth largest air force.

[29] In May 1946, he joined the Australian Battlefields Memorial Committee, convened to advise the Federal government regarding commemoration of the armed forces for their wartime achievements.

[32] Other senior commanders and veterans of the Australian Flying Corps had been summarily retired in 1946, a "purge" that was ostensibly designed to make way for the advancement of younger and equally proficient officers.

Against a harsh post-war economic climate, Mackinolty personally intervened to improve the planned accommodation for trainees, arguing that the youths could not be expected to live in the austere conditions to which other members of the Air Force were used.

[34] Shortly after the first intake of engineer apprentices in January 1948, Mackinolty formally proposed that a similar scheme be set up for apprenticeships in the supply and clerical trades.