sensors Mode-S transponder

840D81

ICAO 24-bit transponder address · allocated to Japan

Currently assigned to JA03RK · BOEING 737-800

Hex
840D81
Octal
41006601
Decimal
8,654,209
Country
JP
Tail
JA03RK
Type
B738
No current signal · last broadcast 17h ago
Flights observed
8
Distinct callsigns
7
Country
JP
Last broadcast
17h ago

Last known position

Most recent position reported by Mode-S 840D81.

Country allocation

The ICAO 24-bit address 840D81 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 7 distinct

Callsign Airline Flights Last seen
JTA53 - 2 2026-04-13
JTA614 Japan Transocean Air 1 2026-04-14
JTA47 - 1 2026-04-13
JTA44 Japan Transocean Air 1 2026-04-14
JTA42 - 1 2026-04-13
JTA128 - 1 2026-04-13
JTA121 - 1 2026-04-13

Recent flights last 8

DateFlightRouteTakeoffLandingDuration
2026-04-14 JTA44 OKA → NGO Apr 14, 07:25 UTCApr 14, 07:40 UTC15m
2026-04-14 JTA614 ISG → OKA Apr 14, 06:00 UTCApr 14, 06:10 UTC10m
2026-04-13 JTA121 - Apr 13, 23:00 UTCApr 13, 23:15 UTC15m
2026-04-13 JTA128 - Apr 13, 11:35 UTCApr 13, 11:55 UTC20m
2026-04-13 JTA47 - Apr 13, 08:20 UTCApr 13, 08:40 UTC20m
2026-04-13 JTA42 - Apr 13, 04:00 UTCApr 13, 04:15 UTC15m
2026-04-13 JTA53 - Apr 13, 01:40 UTCApr 13, 02:00 UTC20m
2026-04-13 JTA53 - Apr 13, 00:45 UTCApr 13, 00:55 UTC10m

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 JA03RK page for operator, model, and routing details .

Mode-S 840D81 frequently asked

What is Mode-S code 840D81?
840D81 is an ICAO 24-bit transponder address. Allocated to Japan. Assigned to JA03RK.
Where is Mode-S 840D81 registered?
Mode-S code 840D81 is allocated to Japan (JP). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 840D81 broadcasting right now?
No active broadcast right now. Last signal was 17h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 840D81, octal 41006601, decimal 8,654,209.
What flights does 840D81 operate?
Mode-S 840D81 has broadcast 7 distinct callsigns, including JTA53, JTA614, JTA47, JTA44, JTA42.