That's LADD (Limited Aircraft Data Displayed), which requires that aircraft marked as such in the FAA's database to be removed from the official data feeds used by the commercial flight radar sites.
Crowdsourced data isn't subject to LADD, so adsbexchange and other such sites can and do display such aircraft.
For flights within the US, there's also a private address program that allows an ADS-B equipped plane to broadcast an alternate address.
Crowdsourced data isn't subject to LADD, so adsbexchange and other such sites can and do display such aircraft.
For flights within the US, there's also a private address program that allows an ADS-B equipped plane to broadcast an alternate address.
https://www.faa.gov/air_traffic/technology/equipadsb/privacy