ICAO 24-Bit Address Explained

An ICAO 24-bit address, also called the Mode S code or hex code, is a unique six-character code assigned to each aircraft’s transponder. It identifies the aircraft in every ADS-B and Mode S message.

How it looks

It is written in hexadecimal, such as 7609EB. There are about 16.7 million possible addresses. The aircraft keeps the address unless it is re-registered or the transponder is reprogrammed.

How addresses are allocated

The International Civil Aviation Organization divides addresses into blocks and gives each country a block. Aircraft registered in that country receive addresses from the block. Pakistani aircraft addresses fall in the 760000 to 767FFF range, so on the live map an aircraft whose code starts with 76 is likely to be registered in Pakistan. Our live map shows the “registered in” country, which is derived from the address block.

What the address tells you and what it does not

It tells you the country of registration, not the airline’s home country and not the aircraft’s current route. It is not the same as the registration (such as AP-XXX), though one can be looked up from the other in databases. See why Pakistani aircraft registrations start with AP-.

Why it matters for trackers

Every message uses the address, so receivers can combine messages from the same aircraft even if the callsign changes. Photos and details on this site are looked up by this address.

General information only, not legal or safety advice. Details change; check with your airline and the relevant authority. See our editorial policy.