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sensors Mode-S transponder

8991A4

ICAO 24-bit transponder address · allocated to Taiwan

Currently assigned to B-18725 · BOEING 747-400

Hex
8991A4
Octal
42310644
Decimal
9,015,716
Country
TW
Tail
B-18725
Type
B744
Broadcasting now · callsign CAL5998 · 2,000 ft
Flights observed
237
Distinct callsigns
20
Country
TW
Last broadcast
7h ago

Current position

8991A4 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address 8991A4 falls within the block assigned to Taiwan (TW) by ICAO Annex 10, Volume III. Every aircraft registered in Taiwan 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
CAL5267 - 15 2026-06-29
CAL5266 - 15 2026-06-26
CAL5265 - 15 2026-06-27
CAL6865 - 8 2026-07-04
CAL5268 - 8 2026-06-28
CAL5239 - 8 2026-07-13
CAL5233 - 8 2026-06-16
CAL5927 - 7 2026-07-02
CAL5240 - 7 2026-07-13
CAL5226 China Airlines 7 2026-04-16
CAL5225 China Airlines 7 2026-04-17
CAL5928 - 6 2026-07-02
CAL5884 - 6 2026-07-08
CAL5234 - 6 2026-06-15
CAL6881 - 5 2026-07-07
CAL5898 - 5 2026-07-04
CAL5878 China Airlines 5 2026-06-22
CAL5637 - 5 2026-07-09
CAL6888 - 4 2026-07-05
CAL6887 - 4 2026-07-05

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 CAL5997 - Jul 14, 20:40 UTCJul 14, 21:45 UTC1h 5m
2026-07-14 CAL5586 - Jul 14, 16:35 UTCJul 14, 17:50 UTC1h 15m
2026-07-14 CAL5586 - Jul 14, 13:35 UTCJul 14, 13:45 UTC10m
2026-07-14 CAL5871 - Jul 14, 09:55 UTCJul 14, 10:15 UTC20m
2026-07-14 CAL5871 - Jul 14, 06:25 UTCJul 14, 07:25 UTC1h 0m
2026-07-13 CAL5239 ANC → TPE Jul 13, 17:05 UTCJul 14, 02:10 UTC9h 5m
2026-07-13 CAL5239 ORD → ANC Jul 13, 09:45 UTCJul 13, 15:25 UTC5h 40m
2026-07-13 CAL5240 ANC → ORD Jul 13, 00:25 UTCJul 13, 05:40 UTC5h 15m
2026-07-12 CAL5240 TPE → ANC Jul 12, 14:05 UTCJul 12, 22:45 UTC8h 40m
2026-07-12 CAL5239 - Jul 12, 09:55 UTCJul 12, 10:25 UTC30m
2026-07-12 CAL5239 - Jul 12, 01:25 UTCJul 12, 08:50 UTC7h 25m
2026-07-11 CAL5239 ORD → ANC Jul 11, 10:20 UTCJul 11, 15:55 UTC5h 35m
2026-07-10 CAL5240 ANC → ORD Jul 10, 20:30 UTCJul 11, 02:00 UTC5h 30m
2026-07-10 CAL5240 TPE → ANC Jul 10, 10:20 UTCJul 10, 19:00 UTC8h 40m
2026-07-10 CAL5640 DEL → TPE Jul 10, 00:25 UTCJul 10, 06:15 UTC5h 50m
2026-07-09 CAL5640 LUX → DEL Jul 9, 15:20 UTCJul 9, 22:35 UTC7h 15m
2026-07-09 CAL5637 - Jul 9, 03:55 UTCJul 9, 12:00 UTC8h 5m
2026-07-08 CAL5637 - Jul 8, 19:50 UTCJul 9, 01:40 UTC5h 50m
2026-07-08 CAL5884 BKK → TPE Jul 8, 04:35 UTCJul 8, 08:10 UTC3h 35m
2026-07-08 CAL5884 - Jul 8, 00:30 UTCJul 8, 02:30 UTC2h 0m
2026-07-07 CAL5883 - Jul 7, 21:25 UTCJul 7, 21:45 UTC20m
2026-07-07 CAL5883 - Jul 7, 18:00 UTCJul 7, 18:40 UTC40m
2026-07-07 CAL6882 - Jul 7, 09:55 UTCJul 7, 14:25 UTC4h 30m
2026-07-07 CAL6881 - Jul 7, 06:50 UTCJul 7, 07:30 UTC40m
2026-07-07 CAL6881 - Jul 7, 00:40 UTCJul 7, 04:25 UTC3h 45m
2026-07-06 CAL5896 - Jul 6, 19:25 UTCJul 6, 20:55 UTC1h 30m
2026-07-06 CAL5895 - Jul 6, 14:25 UTCJul 6, 15:10 UTC45m
2026-07-06 CAL6596 - Jul 6, 10:00 UTCJul 6, 11:30 UTC1h 30m
2026-07-06 CAL6596 - Jul 6, 09:10 UTCJul 6, 09:20 UTC10m
2026-07-06 CAL6596 - Jul 6, 04:20 UTCJul 6, 05:20 UTC1h 0m
2026-07-06 CAL6596 - Jul 6, 03:40 UTCJul 6, 03:50 UTC10m
2026-07-06 CAL6595 - Jul 6, 01:25 UTCJul 6, 01:35 UTC10m
2026-07-05 CAL6595 - Jul 5, 21:45 UTCJul 5, 22:45 UTC1h 0m
2026-07-05 CAL6888 - Jul 5, 17:35 UTCJul 5, 19:05 UTC1h 30m
2026-07-05 CAL6888 - Jul 5, 16:45 UTCJul 5, 16:55 UTC10m
2026-07-05 CAL6887 - Jul 5, 13:40 UTCJul 5, 13:50 UTC10m
2026-07-05 CAL6887 - Jul 5, 11:15 UTCJul 5, 12:00 UTC45m
2026-07-05 CAL5834 HKG → TPE Jul 5, 07:15 UTCJul 5, 08:35 UTC1h 20m
2026-07-05 CAL5833 - Jul 5, 04:25 UTCJul 5, 04:40 UTC15m
2026-07-05 CAL5833 - Jul 5, 03:30 UTCJul 5, 03:50 UTC20m
2026-07-04 CAL5898 TPE → TPE Jul 4, 16:45 UTCJul 5, 00:10 UTC7h 25m
2026-07-04 CAL6866 - Jul 4, 12:35 UTCJul 4, 13:50 UTC1h 15m
2026-07-04 CAL6866 - Jul 4, 09:35 UTCJul 4, 09:45 UTC10m
2026-07-04 CAL6865 - Jul 4, 05:45 UTCJul 4, 06:40 UTC55m
2026-07-04 CAL6865 - Jul 4, 02:50 UTCJul 4, 03:10 UTC20m
2026-07-03 CAL6865 - Jul 3, 23:25 UTCJul 4, 00:20 UTC55m
2026-07-03 CAL6876 - Jul 3, 14:30 UTCJul 3, 16:40 UTC2h 10m
2026-07-03 CAL6876 - Jul 3, 09:05 UTCJul 3, 11:55 UTC2h 50m
2026-07-03 CAL6875 - Jul 3, 06:30 UTCJul 3, 06:55 UTC25m
2026-07-03 CAL6875 - Jul 3, 02:50 UTCJul 3, 03:40 UTC50m

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 B-18725 page for operator, model, and routing details .

Mode-S 8991A4 frequently asked

What is Mode-S code 8991A4?
8991A4 is an ICAO 24-bit transponder address. Allocated to Taiwan. Assigned to B-18725.
Where is Mode-S 8991A4 registered?
Mode-S code 8991A4 is allocated to Taiwan (TW). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 8991A4 broadcasting right now?
Yes. Mode-S 8991A4 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 8991A4, octal 42310644, decimal 9,015,716.
What flights does 8991A4 operate?
Mode-S 8991A4 has broadcast 20 distinct callsigns, including CAL5267, CAL5266, CAL5265, CAL6865, CAL5268.