Missing Identification from Raw data

Hi,

I’m seeing many messages without Aircraft Identification as shown in the attached screenshot. I tried to find the official documentation for ADS-B with no luck. so i’m not sure why these messages are missing some information.

Appreciate if someone can explain.

Antoine

They are not required. ATC use the ICAO address.

The “Ident” is programmed in the transponder by the pilot. It can be blank. Or, your receiver may not have received the Ident message yet, but has received other messages such as positions. Learn more about Idents here:
https://mailchi.mp/flightaware/ads-b-network-news-2017-july
https://mailchi.mp/flightaware/making-sense-of-strange-ads-b-data