sensors Mode-S transponder

71C556

ICAO 24-bit transponder address · allocated to Korea, South

Currently assigned to HL8556 · AIRBUS A-321neo

Hex
71C556
Octal
34342526
Decimal
7,456,086
Country
KR
Tail
HL8556
Type
A21N
No current signal · last broadcast 12h ago
Flights observed
7
Distinct callsigns
5
Country
KR
Last broadcast
12h ago

Last known position

Most recent position reported by Mode-S 71C556.

Country allocation

The ICAO 24-bit address 71C556 falls within the block assigned to Korea, South (KR) by ICAO Annex 10, Volume III. Every aircraft registered in Korea, South receives a permanent address from this block at the time of registration; the address stays with the airframe even if the aircraft is re-registered to a different operator within the country.

Callsign history 5 distinct

Callsign Airline Flights Last seen
KAL743 - 2 2026-04-13
KAL712 - 2 2026-04-14
KAL792 - 1 2026-04-13
KAL791 Korean Air 1 2026-04-13
KAL711 - 1 2026-04-14

Recent flights last 7

DateFlightRouteTakeoffLandingDuration
2026-04-14 KAL712 - Apr 14, 09:10 UTCApr 14, 11:00 UTC1h 50m
2026-04-14 KAL712 - Apr 14, 08:40 UTCApr 14, 09:05 UTC25m
2026-04-14 KAL711 - Apr 14, 05:25 UTCApr 14, 06:20 UTC55m
2026-04-13 KAL743 - Apr 13, 11:45 UTCApr 13, 11:55 UTC10m
2026-04-13 KAL743 - Apr 13, 10:35 UTCApr 13, 11:05 UTC30m
2026-04-13 KAL792 - Apr 13, 06:10 UTCApr 13, 07:05 UTC55m
2026-04-13 KAL791 ICN → FUK Apr 13, 02:25 UTCApr 13, 02:55 UTC30m

About Mode-S

A Mode-S transponder code (also called an "ICAO 24-bit address" or "hex code") is a 6-character hexadecimal identifier permanently assigned to an aircraft when it's first registered. Unlike callsigns (which change with each flight) or registrations (which can change if an aircraft is sold internationally), the Mode-S address stays with the airframe for the life of the aircraft in that country.

Every ADS-B transmission from an aircraft includes its Mode-S address, making it the most reliable way to identify a specific airframe. Flight-tracking services like Apparatus use the Mode-S address as the primary key for tying position broadcasts, callsigns, and ownership records together.

Prefer a tail-number view? See the HL8556 page for operator, model, and routing details .

Mode-S 71C556 frequently asked

What is Mode-S code 71C556?
71C556 is an ICAO 24-bit transponder address. Allocated to Korea, South. Assigned to HL8556.
Where is Mode-S 71C556 registered?
Mode-S code 71C556 is allocated to Korea, South (KR). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 71C556 broadcasting right now?
No active broadcast right now. Last signal was 12h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 71C556, octal 34342526, decimal 7,456,086.
What flights does 71C556 operate?
Mode-S 71C556 has broadcast 5 distinct callsigns, including KAL743, KAL712, KAL792, KAL791, KAL711.