FlightAware Discussions

ICAO numbers

What is the meaning of an ICAO number starting with something other than A (United States registration) or C (Canadian registration)? Specifically, my feeder shows a lot of aircraft (all captured through TIS-B) with ICAO numbers (or at least it is in that field of the report from the feeder) starting with 298 (for example, 29870F is a helicopter that has been hovering over my house for 30 minutes). Does TIS-B create pseudo numbers that fill this field on the PIAware web page? Are they trackable in any way?

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TIS-B appears to be random, or a range allocated to a ground station.
ADS-R should use the original ICAO hex code.

The bulk of the TIS-B showing up on my feed start with 2F8. I presume that these are from a tower near Newark (EWR). I sometimes see them on the ground in LGA and JFK. I am very low and fairly shielded from LGA and JFK. It just depends on aircraft and the weather.

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Thanks Jon—that is a helpful article on the FAA web site. I see now the TIS-B codes seem to be airport related—I see a whole lot of 318xxx that are all on the ground at LAX and then some 298xxx which are probably coming from the Point Mugu approach facility (20 miles from me). One thing I think I see is that the codes seem to change for the same aircraft — the helicopter that has been hovering seems to go in and out of radar coverage and each time it returns to my feeder it has a new code, so I’m guessing these codes are not trackable (or at least not trackable unless you have some compelling reason for the FAA to dig through their logs to tie a code to an aircraft at a particular point in time).

It sounds like the helo is squawking 1200 or a generic Mode C code. There could be many in the area and make them hard the distinguish.

More generally, for actual (non-TIS-B) ICAO addresses, that’s not really what the A and C mean. There is a range of addresses allocated to each country. USA happens to have A00000 - AFFFFF i.e. all possible addresses starting with A, so “A = USA registration” is accurate; but there are several countries that have ranges that start with “C” (Canada, NZ, Fiji, Tonga, Vanuatu, …).

These country address ranges are how skyview decides on the flag to show.