> Which would make the identifier itself, and its real-time location, public information, but the knowledge of who owns the identifier would remain as private information.

Yes and no. Tracking airplanes is something hobbyists have been doing for decades; there are people who hang out by airports and record every flight in and out. The PIA program can be useful for realtime masking but the information is far from secret — nor should it be, imo.

> "Elon Musk, for example, has a Gulfstream and there's only so many people that fly that particular plane out of Brownsville, Texas and fly to the same airports," Sweeney told Insider.

> ...

> "These privacy mitigation programs are effective for real-time operations but do not guarantee absolute privacy," an FAA spokesperson said. "A flight can still be tracked in other ways such as a Freedom of Information Act request, www.LiveATC.com, ADSB Exchange, or a frequently departed airport."

https://www.businessinsider.com/elon-musk-appears-use-faa-to...