 On 1 April 1954, Mukerjee took over as the Commander-in-Chief of the Indian Air Force, with the rank of Air Marshal.When the Change in Designation Act, 1955, was passed, the title of "Commander-in-Chief" was replaced by Chief of the Air Staff (CAS).Thus Mukerjee became the first Indian Commander-in-Chief as well as Chief of Air Staff of the Indian Air Force.