sensors Mode-S transponder
71A921
ICAO 24-bit transponder address · allocated to Korea, South
Currently assigned to HL5121
- Hex
- 71A921
- Octal
- 34324441
- Decimal
- 7,448,865
- Country
- KR
- Tail
- HL5121
- Type
- C208
- Flights observed
- 67
- Distinct callsigns
- 1
- Country
- KR
- Last broadcast
- 3d ago
Last known position
Country allocation
The ICAO 24-bit address 71A921 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 1 distinct
| Callsign | Airline | Flights | Last seen |
|---|---|---|---|
| HL5121 | - | 67 | 2026-07-11 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-11 | HL5121 | - | Jul 11, 02:50 UTC | Jul 11, 03:20 UTC | 30m |
| 2026-07-10 | HL5121 | - | Jul 10, 23:05 UTC | Jul 10, 23:45 UTC | 40m |
| 2026-06-28 | HL5121 | - | Jun 28, 01:34 UTC | Jun 28, 02:10 UTC | 35m |
| 2026-06-27 | HL5121 | - | Jun 27, 23:00 UTC | Jun 27, 23:34 UTC | 35m |
| 2026-06-27 | HL5121 | - | Jun 27, 08:44 UTC | Jun 27, 09:09 UTC | 25m |
| 2026-06-27 | HL5121 | - | Jun 27, 04:59 UTC | Jun 27, 05:29 UTC | 30m |
| 2026-06-27 | HL5121 | - | Jun 27, 03:20 UTC | Jun 27, 03:55 UTC | 35m |
| 2026-06-26 | HL5121 | - | Jun 26, 23:04 UTC | Jun 26, 23:44 UTC | 40m |
| 2026-06-23 | HL5121 | - | Jun 23, 22:25 UTC | Jun 24, 00:15 UTC | 1h 50m |
| 2026-06-15 | HL5121 | - | Jun 15, 22:49 UTC | Jun 16, 02:00 UTC | 3h 10m |
| 2026-06-13 | HL5121 | - | Jun 13, 03:55 UTC | Jun 13, 04:25 UTC | 30m |
| 2026-06-12 | HL5121 | - | Jun 12, 22:55 UTC | Jun 12, 23:25 UTC | 30m |
| 2026-06-12 | HL5121 | PUS → GMP | Jun 12, 05:45 UTC | Jun 12, 07:35 UTC | 1h 50m |
| 2026-06-12 | HL5121 | - | Jun 12, 00:10 UTC | Jun 12, 01:00 UTC | 51m |
| 2026-06-06 | HL5121 | - | Jun 6, 07:50 UTC | Jun 6, 08:20 UTC | 30m |
| 2026-06-06 | HL5121 | - | Jun 6, 04:45 UTC | Jun 6, 05:20 UTC | 35m |
| 2026-06-05 | HL5121 | - | Jun 5, 22:00 UTC | Jun 6, 02:25 UTC | 4h 25m |
| 2026-06-01 | HL5121 | - | Jun 1, 01:55 UTC | Jun 1, 02:25 UTC | 30m |
| 2026-05-31 | HL5121 | - | May 31, 21:55 UTC | May 31, 22:25 UTC | 30m |
| 2026-05-31 | HL5121 | - | May 31, 08:35 UTC | May 31, 08:50 UTC | 15m |
| 2026-05-30 | HL5121 | - | May 30, 23:50 UTC | May 31, 00:05 UTC | 15m |
| 2026-05-30 | HL5121 | - | May 30, 22:05 UTC | May 30, 23:10 UTC | 1h 5m |
| 2026-05-30 | HL5121 | - | May 30, 04:10 UTC | May 30, 08:30 UTC | 4h 20m |
| 2026-05-29 | HL5121 | - | May 29, 22:00 UTC | May 30, 02:35 UTC | 4h 35m |
| 2026-05-19 | HL5121 | - | May 19, 00:30 UTC | May 19, 01:45 UTC | 1h 15m |
| 2026-05-18 | HL5121 | - | May 18, 22:45 UTC | May 18, 23:35 UTC | 50m |
| 2026-05-17 | HL5121 | - | May 17, 08:30 UTC | May 17, 09:50 UTC | 1h 20m |
| 2026-05-17 | HL5121 | - | May 17, 04:25 UTC | May 17, 05:50 UTC | 1h 25m |
| 2026-05-16 | HL5121 | - | May 16, 08:31 UTC | May 16, 09:25 UTC | 55m |
| 2026-05-16 | HL5121 | - | May 16, 04:35 UTC | May 16, 05:35 UTC | 1h 0m |
| 2026-05-08 | HL5121 | - | May 8, 22:00 UTC | May 9, 02:30 UTC | 4h 30m |
| 2026-05-08 | HL5121 | - | May 8, 08:05 UTC | May 8, 08:40 UTC | 35m |
| 2026-05-08 | HL5121 | - | May 8, 04:04 UTC | May 8, 04:25 UTC | 20m |
| 2026-05-01 | HL5121 | - | May 1, 09:50 UTC | May 1, 13:30 UTC | 3h 40m |
| 2026-05-01 | HL5121 | - | May 1, 02:10 UTC | May 1, 02:40 UTC | 30m |
| 2026-04-30 | HL5121 | - | Apr 30, 22:15 UTC | Apr 30, 22:40 UTC | 25m |
| 2026-04-30 | HL5121 | - | Apr 30, 01:45 UTC | Apr 30, 02:15 UTC | 30m |
| 2026-04-30 | HL5121 | - | Apr 30, 00:40 UTC | Apr 30, 01:15 UTC | 35m |
| 2026-04-29 | HL5121 | - | Apr 29, 21:30 UTC | Apr 29, 22:00 UTC | 30m |
| 2026-04-28 | HL5121 | - | Apr 28, 10:40 UTC | Apr 28, 11:40 UTC | 1h 0m |
| 2026-04-28 | HL5121 | - | Apr 28, 07:05 UTC | Apr 28, 08:00 UTC | 55m |
| 2026-04-26 | HL5121 | - | Apr 26, 10:40 UTC | Apr 26, 11:35 UTC | 55m |
| 2026-04-26 | HL5121 | - | Apr 26, 07:00 UTC | Apr 26, 07:30 UTC | 30m |
| 2026-04-24 | HL5121 | - | Apr 24, 23:00 UTC | Apr 25, 02:10 UTC | 3h 10m |
| 2026-04-21 | HL5121 | - | Apr 21, 04:15 UTC | Apr 21, 08:40 UTC | 4h 25m |
| 2026-04-21 | HL5121 | - | Apr 21, 01:30 UTC | Apr 21, 02:55 UTC | 1h 25m |
| 2026-04-20 | HL5121 | - | Apr 20, 22:15 UTC | Apr 21, 00:50 UTC | 2h 35m |
| 2026-04-19 | HL5121 | - | Apr 19, 12:20 UTC | Apr 19, 13:15 UTC | 55m |
| 2026-04-19 | HL5121 | - | Apr 19, 10:50 UTC | Apr 19, 11:50 UTC | 1h 0m |
| 2026-04-18 | HL5121 | - | Apr 18, 22:35 UTC | Apr 19, 02:45 UTC | 4h 10m |
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 HL5121 page for operator, model, and routing details .