sensors Mode-S transponder

71C523

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

Currently assigned to HL8523 · BOEING 737 MAX 8

Hex
71C523
Octal
34342443
Decimal
7,456,035
Country
KR
Tail
HL8523
Type
B38M
Broadcasting now · callsign JJA2504 · 21,175 ft
Flights observed
7
Distinct callsigns
6
Country
KR
Last broadcast
13h ago

Current position

71C523 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address 71C523 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 6 distinct

Callsign Airline Flights Last seen
JJA1802 - 2 2026-04-14
JJA8402 - 1 2026-04-13
JJA1801 - 1 2026-04-14
JJA1301 Jeju Air 1 2026-04-13
JJA1106 - 1 2026-04-13
JJA1105 - 1 2026-04-13

Recent flights last 7

DateFlightRouteTakeoffLandingDuration
2026-04-14 JJA1802 - Apr 14, 09:10 UTCApr 14, 09:45 UTC35m
2026-04-14 JJA1802 - Apr 14, 08:05 UTCApr 14, 08:15 UTC10m
2026-04-14 JJA1801 - Apr 14, 05:15 UTCApr 14, 06:30 UTC1h 15m
2026-04-13 JJA1301 KIX → ICN Apr 13, 22:30 UTCApr 13, 23:30 UTC1h 0m
2026-04-13 JJA1106 - Apr 13, 08:20 UTCApr 13, 10:20 UTC2h 0m
2026-04-13 JJA1105 - Apr 13, 04:35 UTCApr 13, 06:35 UTC2h 0m
2026-04-13 JJA8402 - Apr 13, 02:50 UTCApr 13, 03:10 UTC20m

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 HL8523 page for operator, model, and routing details .

Mode-S 71C523 frequently asked

What is Mode-S code 71C523?
71C523 is an ICAO 24-bit transponder address. Allocated to Korea, South. Assigned to HL8523.
Where is Mode-S 71C523 registered?
Mode-S code 71C523 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 71C523 broadcasting right now?
Yes. Mode-S 71C523 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 71C523, octal 34342443, decimal 7,456,035.
What flights does 71C523 operate?
Mode-S 71C523 has broadcast 6 distinct callsigns, including JJA1802, JJA8402, JJA1801, JJA1301, JJA1106.