When is squawk 1000 assigned in USA? From Are squawk codes used with ADS-B?:


  Yes, squawk codes are still used and required with ADS-B.


The post is 3 years old though. And from Wikipedia List of transponder codes:


  1000: Used exclusively by ADS-B aircraft to inhibit Mode 3A transmit (USA)


The way I understand that, if the flight will be in complete ADS-B coverage, say a domestic flight, it is assigned 1000.

Is 1000 indeed assigned to ADS-B flights, or are they given discrete* codes still?



* Oops. I didn't mean discrete as in hex discrete, but the 4-digit one that changes from flight to flight.
Currently, FAA's "fusion" software uses discrete squawk codes to merge targets generated by different surveillance systems, i.e. SSR (often several of them) and ADS-B. They plan to upgrade the software so it can merge targets based on Mode S hex code as well, but (as of early 2019) that hasn't been rolled out yet. Once that is in place, ATC will switch to telling Mode S targets to squawk 1000. Mode A/C targets will still need discrete codes, though, including Mode S aircraft in areas that only have Mode C SSR.