Free tool
ICAO address converter
Paste a 24-bit aircraft address and get the tail number and country. In many countries the address encodes the tail number as arithmetic. Other countries require a database lookup.
One or a whole list. Any separator works.
Or click an example
Paste an address above, or try one of the examples. The message decoder will give you an address out of a raw message.
How this works
- Where the tail number is in the address
- The FAA does not pick an address and write it down next to a tail number. The FAA calculates it. Addresses A00001 through ADF7C7 map directly to N1 through N99999. The address and the tail number represent the same information. Change the tail number and the address changes with it. Canada, Japan, South Korea, France, Germany and about a dozen more countries use the same kind of arithmetic with their own ranges.
The US block starts at address A00001.
Base = 0xA00001The first digit after N picks a stride of 101,711 addresses. N1 starts at offset 0.
(1 − 1) × 101,7110Each further digit skips 601 letter-suffix codes and picks the next stride.
601 + 2 × 10,111+ 20,823Third digit.
601 + 3 × 951+ 3,454Fourth digit.
601 + 4 × 35+ 741A fifth digit sits after the 25 letter-suffix slots.
25 + 5+ 30The total offset from the base is 25,048.
0xA00001 + 25,048= 0xA061D9- Registered addresses
- Most countries assign addresses from a register. The address does not encode the tail number, and there is no arithmetic to run. A register lookup is less reliable than a computation. The database stays correct only until someone re-registers the aircraft. The address can stay the same after re-registration.
- What an address identifies
- The 24 bits belong to the airframe, not to the flight. One aircraft broadcasts the same address on every trip, which is how a receiver can follow it through a whole day. If you re-register the aircraft, the tail marks change. In most countries, the address stays the same.
N12345→A061D9
Frequently asked questions
- What is a 24-bit ICAO aircraft address?
- A 24-bit ICAO aircraft address is a unique hexadecimal number that identifies each aircraft. The transponder broadcasts this address in every Mode S and ADS-B message. It has 16,777,216 possible values (2 to the power of 24) and takes six hex characters to write.
- How do I look up an aircraft by hex address?
- Enter the six hex characters into the tool above. For addresses in the US, Canadian, Japanese, and other arithmetic ranges, the tool calculates the tail number directly. For register-based countries, it checks available databases.
- What is the difference between a hex address and a tail number?
- The tail number is the registration painted on the fuselage. The hex address is a binary number the transponder broadcasts. In the US and about twenty other countries, one is a mathematical encoding of the other. In most other countries, the authority assigns them independently.
- Why does my hex address start with A?
- Addresses that start with A (from A00001 through ADF7C7) belong to the United States. ICAO allocated this range to the FAA. The first hex character tells you the country or region that registered the aircraft.
- Can I use the hex address to track a specific aircraft?
- Yes. The hex address stays the same across every flight, so tracking sites and ADS-B receivers use it to follow one aircraft over time. Enter the address on sites like ADS-B Exchange or FlightAware to see current and historical positions.
- What happens to the hex address when an aircraft changes countries?
- The aircraft gets a new address from the new country's allocated range. The original country reclaims the old address. This is why historical tracking data sometimes shows an address linked to a different aircraft than the one that broadcasts it today.
- What is the difference between a hex address, a registration, and a callsign?
- The hex address is the 24-bit transponder identity. It is assigned to the airframe and stays the same across every flight. The registration (tail number) is the alphanumeric marking painted on the fuselage, like N12345 or G-ABCD. In many countries the hex address encodes the registration, but they are separate identifiers. The callsign is the radio identifier for a specific flight, like UAL123 or CESSNA 9ER. It changes every flight and is broadcast in the ADS-B callsign field (type code 1–4). A flight tracker shows all three for the same aircraft.A835AF hexN12345 registrationUAL123 callsign
- What are temporary or anonymized ICAO addresses?
- ICAO reserves the range F00000 through F3FFFF for temporary addresses. These are used by aircraft participating in privacy programs, such as the FAA's LADD (Limiting Aircraft Data Displayed) or PIA (Privacy ICAO Address) program. A temporary address rotates periodically and cannot be resolved to a tail number through arithmetic or a database lookup. If you see an address in the F0xxxx range and the tool returns no result, the aircraft is deliberately anonymized.
F00000 – F3FFFF → temporary / PIA range
You just decoded one aircraft's 24-bit address.
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