Hex Code starting character

I was wondering if anyone knows why some of the hex codes in the aircraft.json start with the “~” sign. Are those the anonomized flights? Thanks in advance.

ICAO assigns blocks of mode-S codes to countries and then the countries assign mode-S codes to individual transponders/planes. ~ means that the mode-S code is not an ICAO assigned code.
These planes are usually TIS-B.

I think there was an ADSB newsletter about TIS-B and ICAO registrations.

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those are aircrafts via mlat where flightaware anonymized the aircraft …

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Thanks. Appreciate the help.

I am not sure now based on the feedback from FA. Thanks for the help.

Anonymized MLAT are mapped onto unassigned blocks of ICAO address. Blocks of mode-S that have’t been assigned to a country.

So tom is correct that ~ does include these types of planes.

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Appreciate the help again! Just trying to understand the way this all works. Looking forward to making some Skyview customizations next!