NextGen[1] is the result of the Vision 100 – Century of Aviation Reauthorization Act[2] to modernize the National Aviation System to increase safety and efficiency. Such modernization includes the FAA’s Automatic Dependent Surveillance–Broadcast (ADS–B) Out rule[3] which requires ADS-B Out capability in certain airspace per 14 CFR § 91.225. ADS-B surveillance allows ATC to track aircraft more accurately through a network of ground stations.
ADS-B Out operates by transmitting unencrypted aircraft data, including identification data such as the aircraft’s unique ICAO code and flight ID (call sign or the N-number). That data can be received by anyone with appropriate equipment. To mitigate this concern, the FAA initiated the Privacy ICAO Address program (PIA[4]). Currently only 1090 MHz ADS-B equipped aircraft are eligible to apply. For operators equipped with 978 UAT, they may check with their avionics shop for options on operating in anonymous mode. For privacy, PIA requires the operator to use a third-party call sign from a provider with a security agreement with FAA. The frequently asked questions section on the FAA PIA website provides information on obtaining third-party call signs. For further information, the PIA user guide[5] provides guidance on eligibility.
In addition, the FAA Limiting Aircraft Data Displayed (LADD[6]) program is designed to block the shared data that the FAA transmits over the internet. The LADD Source Blocking option offers enhanced privacy by limiting the data to FAA use only. If you would like to track your own aircraft through a vendor, you may opt for the Subscriber Level blocking option which binds the vendors not to publicly display your aircraft information. You may still obtain your specific flight tracking information directly from the vendor. Operators may submit a LADD blocking request online, by email to LADD@FAA.GOV, or by mail.
https://pilot-protection-services.aopa.org/news/2021/december/01/flight-tracking-and-privacy