Its lucky sign. They had it on Tu-142, they are having it on p8-i. I believe they will have it on next generation a/c. Indians are superstitious!The two letter code is used by the Air National Guard to identify the base and its not used across USAF. USAF Wings such as the fighting first and Wolf Pack, wings with a glorious past have their own two letter designation. Wolf Pack is WP and Fighting First is FF, these tail codes go back to World War II or earlier. The purpose was easy identification of the aircraft from wreckage since the tail often survived the crash. Of course the USAAF had thousands of aircraft in theatre (WWII) so the need for easy identification makes sense. In the case of the the Indian Navy with just eight P8-I's all belonging to the same base the easy identification of wreckage line of thought does not explain the rationale for having the base code marked on the tail. So I repeat my question, why does the Indian Navy need to paint the base code on the tail of the P-8I?