Apparatus

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sensors Mode-S transponder

8681B1

ICAO 24-bit transponder address · allocated to Japan

Currently assigned to JA73NK · BOEING 737-800

Hex
8681B1
Octal
41500661
Decimal
8,815,025
Country
JP
Tail
JA73NK
Type
B738
No current signal · last broadcast Jul 26, 22:15 UTC
Flights observed
559
Distinct callsigns
20
Country
JP
Last broadcast
Jul 26, 22:15 UTC

Last known position

Most recent position reported by Mode-S 8681B1.

Country allocation

The ICAO 24-bit address 8681B1 falls within the block assigned to Japan (JP) by ICAO Annex 10, Volume III. Every aircraft registered in Japan 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 20 distinct

Callsign Airline Flights Last seen
SKY593 - 11 2026-07-16
SKY597 Skymark Airlines 9 2026-07-25
SKY591 Skymark Airlines 9 2026-07-23
SKY726 - 8 2026-07-17
SKY723 - 8 2026-07-17
SKY509 - 8 2026-07-16
SKY768 - 7 2026-06-29
SKY518 - 7 2026-07-17
SKY109 - 7 2026-07-15
SKY795 Skymark Airlines 6 2026-07-21
SKY729 Skymark Airlines 6 2026-07-24
SKY727 - 6 2026-06-29
SKY716 Skymark Airlines 6 2026-07-26
SKY714 - 6 2026-07-15
SKY713 Skymark Airlines 6 2026-07-26
SKY711 - 6 2026-07-15
SKY706 Skymark Airlines 6 2026-07-24
SKY618 - 6 2026-07-24
SKY558 Skymark Airlines 6 2026-07-25
SKY532 Skymark Airlines 6 2026-07-21

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 SKY511 HND → OKA Jul 26, 21:55 UTCJul 26, 22:15 UTC20m
2026-07-26 SKY026 FUK → HND Jul 26, 12:40 UTCJul 26, 14:00 UTC1h 20m
2026-07-26 SKY025 HND → FUK Jul 26, 10:15 UTCJul 26, 11:20 UTC1h 5m
2026-07-26 SKY716 CTS → HND Jul 26, 07:30 UTCJul 26, 08:50 UTC1h 20m
2026-07-26 SKY713 HND → CTS Jul 26, 03:40 UTCJul 26, 04:55 UTC1h 15m
2026-07-26 SKY512 OKA → HND Jul 26, 00:10 UTCJul 26, 02:20 UTC2h 10m
2026-07-25 SKY551 NGO → OKA Jul 25, 21:25 UTCJul 25, 22:55 UTC1h 30m
2026-07-25 SKY558 OKA → NGO Jul 25, 12:05 UTCJul 25, 13:35 UTC1h 30m
2026-07-25 SKY597 UKB → OKA Jul 25, 10:45 UTCJul 25, 11:00 UTC15m
2026-07-25 SKY597 UKB → OKA Jul 25, 09:25 UTCJul 25, 10:00 UTC35m
2026-07-25 SKY613 HND → SHI Jul 25, 02:30 UTCJul 25, 08:35 UTC6h 5m
2026-07-24 SKY706 CTS → HND Jul 24, 23:25 UTCJul 25, 00:35 UTC1h 10m
2026-07-24 SKY729 HND → CTS Jul 24, 13:00 UTCJul 24, 14:20 UTC1h 20m
2026-07-24 SKY618 - Jul 24, 09:40 UTCJul 24, 12:00 UTC2h 20m
2026-07-24 SKY555 NGO → OKA Jul 24, 04:20 UTCJul 24, 05:55 UTC1h 35m
2026-07-24 SKY550 OKA → NGO Jul 24, 01:30 UTCJul 24, 03:00 UTC1h 30m
2026-07-23 SKY591 UKB → OKA Jul 23, 22:45 UTCJul 24, 00:25 UTC1h 40m
2026-07-23 SKY187 - Jul 23, 10:55 UTCJul 23, 11:55 UTC1h 0m
2026-07-23 SKY794 CTS → IBR Jul 23, 09:00 UTCJul 23, 10:05 UTC1h 5m
2026-07-23 SKY765 - Jul 23, 06:45 UTCJul 23, 08:10 UTC1h 25m
2026-07-23 SKY636 KOJ → NGO Jul 23, 04:55 UTCJul 23, 05:40 UTC45m
2026-07-22 SKY131 UKB → KOJ Jul 22, 23:55 UTCJul 23, 00:30 UTC35m
2026-07-22 SKY590 OKA → UKB Jul 22, 21:25 UTCJul 22, 23:05 UTC1h 40m
2026-07-22 SKY523 HND → OKA Jul 22, 10:20 UTCJul 22, 11:50 UTC1h 30m
2026-07-22 SKY185 IBR → UKB Jul 22, 05:15 UTCJul 22, 05:25 UTC10m
2026-07-22 SKY184 UKB → IBR Jul 22, 03:30 UTCJul 22, 04:25 UTC55m
2026-07-22 SKY170 CTS → UKB Jul 22, 01:00 UTCJul 22, 02:35 UTC1h 35m
2026-07-21 SKY171 - Jul 21, 22:35 UTCJul 22, 00:05 UTC1h 30m
2026-07-21 SKY178 - Jul 21, 12:00 UTCJul 21, 13:25 UTC1h 25m
2026-07-21 SKY795 IBR → CTS Jul 21, 09:50 UTCJul 21, 11:00 UTC1h 10m
2026-07-21 SKY532 OKA → IBR Jul 21, 06:50 UTCJul 21, 09:00 UTC2h 10m
2026-07-21 SKY163 UKB → SHI Jul 21, 02:05 UTCJul 21, 03:40 UTC1h 35m
2026-07-21 SKY132 KOJ → UKB Jul 21, 00:20 UTCJul 21, 01:00 UTC40m
2026-07-20 SKY301 HND → KOJ Jul 20, 21:50 UTCJul 20, 22:55 UTC1h 5m
2026-07-20 SKY026 FUK → HND Jul 20, 12:45 UTCJul 20, 14:10 UTC1h 25m
2026-07-20 SKY025 - Jul 20, 10:15 UTCJul 20, 11:20 UTC1h 5m
2026-07-20 SKY720 - Jul 20, 07:35 UTCJul 20, 09:05 UTC1h 30m
2026-07-20 SKY717 - Jul 20, 05:20 UTCJul 20, 06:30 UTC1h 10m
2026-07-20 SKY712 - Jul 20, 02:55 UTCJul 20, 04:15 UTC1h 20m
2026-07-20 SKY175 UKB → CTS Jul 20, 00:25 UTCJul 20, 02:00 UTC1h 35m
2026-07-19 SKY140 - Jul 19, 22:45 UTCJul 19, 23:35 UTC50m
2026-07-19 SKY147 - Jul 19, 10:55 UTCJul 19, 11:45 UTC50m
2026-07-19 SKY113 - Jul 19, 09:10 UTCJul 19, 10:00 UTC50m
2026-07-19 SKY014 - Jul 19, 05:55 UTCJul 19, 07:20 UTC1h 25m
2026-07-19 SKY011 HND → FUK Jul 19, 03:05 UTCJul 19, 04:05 UTC1h 0m
2026-07-19 SKY302 - Jul 19, 00:40 UTCJul 19, 01:55 UTC1h 15m
2026-07-18 SKY635 - Jul 18, 21:50 UTCJul 18, 22:25 UTC35m
2026-07-18 SKY309 - Jul 18, 10:15 UTCJul 18, 13:20 UTC3h 5m
2026-07-18 SKY018 - Jul 18, 07:35 UTCJul 18, 09:10 UTC1h 35m
2026-07-18 SKY015 - Jul 18, 05:00 UTCJul 18, 06:05 UTC1h 5m

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 JA73NK page for operator, model, and routing details .

Mode-S 8681B1 frequently asked

What is Mode-S code 8681B1?
8681B1 is an ICAO 24-bit transponder address. Allocated to Japan. Assigned to JA73NK.
Where is Mode-S 8681B1 registered?
Mode-S code 8681B1 is allocated to Japan (JP). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 8681B1 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 8681B1, octal 41500661, decimal 8,815,025.
What flights does 8681B1 operate?
Mode-S 8681B1 has broadcast 20 distinct callsigns, including SKY593, SKY597, SKY591, SKY726, SKY723.