The ADS-B system assigns a unique 24-bit code (the ICAO address) to every aircraft's transponder. These address assignments are made by national government aviation authorities, such as the United States' Federal Aviation Administration. To determine exactly which aircraft is being tracked, the registration databases can be downloaded from the authorities and used to look up the human-readable identity of the aircraft.
Currently, only the US FAA registry is supported, identifying US-registered civilian aircraft. The current public registry is updated every day, so the YAAC user can download an updated copy of the registry; the downloaded copy is kept with other local YAAC data so it can be used offline.
The menu choice File->Load->Aircraft Database checks the date of the last-downloaded FAA database (if any), and confirms the user wants to download the latest version from the FAA website. Because the FAA website uses secure encrypted HTTP (HTTPS), this menu choice will not be available if use of encrypted HTTPS is disabled in the YAAC configuration.