From the IAF vault: The clever algorithm behind service numbers

Indian Air Force historian Anchit Gupta shares mystery trivia about IAF service numbers

The Indian Air Force service numbers for officers were put in place only in October 1942 -- 10 years after its formation -- and unlike the Royal Air Force/Royal Flying Corps that started with the number 1, the IAF started with the service number 1551. Why 1551 remains a mystery. 

Prior to October 1942, the Air Force Lists only carried the names organized in seniority with no reference to any service number. Possibly, the small size of the IAF did not require an elaborate numbering system.

Through an Air Force order, all officers appearing in the Air Force List of October 1942 were given a service number starting from 1551, in descending order of seniority. Implicitly, officers that died or left prior to October 1942 never had a service number. We counted 93 such officers!

From 1942 to 1950, the service numbers were preceded by the words "IND" to reflect IAF and not confuse it with other commonwealth countries that operated together and had the same commission. On January 26, 1950, the "IND" was dropped.

In the 1980s, IAF added a 'check suffix' to service numbers, an alphabet to avoid confusion when using service numbers for data entry via a crude yet a clever system in the pre-computer era.

Check out the algorithm above