Description

A duplicated Secondary Surveillance Radar (SSR) code is a situation where two (or more) aircraft are squawking the same SSR code while being observable by the same controller.

The primary risk with duplicated SSR codes is that an aircraft could be mis-identified. That is, the controller would believe that a specific track corresponds to a particular aircraft while in reality this would not be the case. Consequently, the controller would issue clearances believing they will be complied with by one aircraft but in fact another one (which may also be in the airspace of another sector) will perform the action.