Third-party apps and websites can lag behind updates. Airlines change codes, new airlines are founded, and old airlines merge. The ICAO Doc 7910 PDF is the official publication. If there is a discrepancy between your flight planning app and Doc 7910, the Doc wins.
ICAO Doc 7910 is the master directory of Location Indicators. In global aviation, places cannot simply be referred to by name; they require a unique, four-letter code to avoid confusion between similar-sounding names and to standardize flight plans, communications, and navigation databases. doc 7910 pdf
If you have ever wondered how "London" becomes EGLL or why "Los Angeles" is KLAX, this is the document that defines those rules. Third-party apps and websites can lag behind updates
This is the most frequently used section of the PDF. It lists every registered airline and operator in the world. The data is organized alphabetically, but crucially, it provides three distinct pieces of information for each entry: Telephony (Radio Call Sign): This is the spoken