[3] In 1922 he, Major W T Blake and Geoffrey Malins made an unsuccessful attempt to fly a Daily News-sponsored round-the-world flight.

The first stage from London to Calcutta was flown in a modified de Havilland DH.9, initially G-EBDE, and subsequently G-EBDL which was later donated to the University of Benares.

The second stage from Calcutta to Vancouver ended with the loss of the aircraft, Fairey IIIC floatplane G-EBDI, in the Bay of Bengal.

The flying journal Aeroplane appeared to have little respect for the expedition, printing a weekly satirical cartoon based on the then popular Adventures of Pip, Squeak and Wilfred serial, as "The Adventures of Mac, Broome and Wilfred", followed by a satirical letter addressed to "My Dear Pilots and Ground Wallahs".

In addition to flying Macmillan wrote numerous magazine articles, as well as books on aviation, including a series detailing the history of the Royal Air Force during the Second World War.

He was also the President of the National League of Airmen, a founder associate member of the Institution of Aeronautical Engineers in 1919, and was made an Associate Fellow of the Royal Aeronautical Society in 1928, and in 1929 was one of the founders of the Guild of Air Pilots and Air Navigators, a first Warden, Deputy Master (1934–35), and a Freeman and Liveryman of the Guild.

[24] Norman Macmillan was married to actress Gladys Mary Peterkin Mitchell ("Pat"; stage name "Ena Beaumont"), Geoffrey Malins' former wife.