Overhead 1090 Explains · Episode 5
Who's flying that?
Updated October 2026
A flight number tells you the route. The aircraft address tells you which airplane is flying it, and a home receiver hears that address in every message.
What's said in the video
Last time: squawk codes. Today: who's flying that? Every plane broadcasts its own address. Six characters. It stays with that airplane. Not the flight number. The airplane itself. Match that address to the registry, and you get the tail number, the type, and who operates it. Overhead 1090 does that for every plane your antenna hears. Search Overhead 1090 on the App Store.
Six characters that belong to the airframe
The address is a 24-bit number, written as six hexadecimal characters such as A1B2C3. You'll also see it called the ICAO address, the Mode S code or the hex code. The country where the aircraft is registered assigns it from its own block of addresses, and it's set in the aircraft's transponder.
It goes with the airframe, not the flight. An airliner that flies four routes in a day has four call signs and one address. The address usually changes only when the aircraft moves to another country's register.
From address to tail number
Aviation registries and community-built databases link each address to a registration (the tail number painted on the aircraft), the aircraft type and the operator. Look up the address and you know which aircraft it is, even when it isn't sending a call sign.
What your own receiver shows
A home receiver decodes the address from every message; that's how it knows which messages belong to which plane. Overhead 1090 matches each address to its registration, type and operator, for every plane your antenna hears, and shows them on the aircraft's card on iPhone, iPad and Apple TV. Episode 4 covers the other code every plane carries, the squawk.
The series
- Ep. 1: What is ADS-B?
- Ep. 2: What does an ADS-B receiver hear?
- Ep. 3: How far can an ADS-B receiver hear?
- Ep. 4: What's a squawk code?
- Ep. 5: Who's flying that?
See every plane over your house on iPhone, iPad and Apple TV: Overhead 1090 on the App Store, one purchase, no subscription.