ICAO: VFR standard squawk code when no other code has been assigned US: External ARTCC subsets (Discrete codes of blocks only except for first primary block, which is used as the ARTCC's non-discrete code if all discrete codes are assigned) Australia: Unmanned aerial vehicle in all classes of airspace and when instructed to enable transponder UK: General conspicuity code Germany: VFR-Flüge ziviler Luftfahrzeuge
SBO