[5] Flying Officer M. J. O'Brian married June Brown on 18 April 1949, at St. Anthony's Church on Empress Road, Lahore.

[6] O'Brian enlisted in the Royal Indian Air Force (RIAF) on 29 April 1946 after graduating the 39 Course of the Initial Training Wing, Pune.

After the Partition of British India, he joined the Royal Pakistan Air Force (RPAF) and participated in the Indo-Pakistani War of 1947.

[3] O'Brian played an important role in setting up the training institutes within the Pakistan Air Force.

[9][10] On 22 April 1976, Commandant O'Brian led the delegation of the National Defence College, Islamabad on a visit to Peking, China where banquets were held by both countries for each other.