The FAA said it is cracking down on improper ADS-B codes in 2018.
Though improperly configured ADS-Bs broadcasting improper hexadecimal codes like 000000 or FFFFFF are nothing new, as of Jan. 2, the FAA has started actively blocking them. The FAA said that, on average, there is a flight per day in the national airspace using one of these codes, despite the fact that none should, and the lack of uniqueness creates potential confusion and safety hazard.
Having their signal blocked also means that pilots broadcasting one of these non-compliant signals will be unable to receive traffic information service — broadcast messages, at least until they are close enough to pick up such ATC services on secondary radar.
Owners and operators can request a check on whether their ADS-B is being filtered by requesting a public ADS-B performance report. They can also check the ICAO code that their aircraft was assigned so that they can make sure it matches that the Mode S code their ADS-B is broadcasting.