This issue surfaced during the development of the specification for the FAA SBS ADS-B Ground Stations. It has been discussed at numerous RTCA SC-186 Plenary and ICAO Aeronautical Surveillance Panel (ASP) Technical Subgroup (TSG) sessions. A note was added in ICAO Doc 9871 §A.2.7.3, which allows manufacturers the option to detect, process and output a duplicate aircraft address flag. DO-260() needs to resolve the issue in the airborne receiver, OR at least insert the same note as in ICAO Doc 9871, thus allowing manufacturers the option to detect, process and output a duplicate aircraft address.