Apparatus

Try JFK, AAL1290, BAW, or N225AN.

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
No current signal · last broadcast 1h ago
Flights observed
73
Distinct callsigns
20
Country
TW
Last broadcast
1h ago

Last known position

Most recent position reported by Mode-S 8991A4.

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 China Airlines 11 2026-04-20
CAL5226 China Airlines 7 2026-04-16
CAL5225 China Airlines 7 2026-04-17
CAL5265 China Airlines 6 2026-05-30
CAL5268 China Airlines 4 2026-04-19
CAL5266 China Airlines 4 2026-05-29
CAL6851 - 3 2026-04-18
CAL5878 - 3 2026-04-14
CAL5231 China Airlines 3 2026-05-26
CAL6875 China Airlines 2 2026-05-22
CAL5927 China Airlines 2 2026-05-19
CAL5898 China Airlines 2 2026-04-17
CAL5827 China Airlines 2 2026-05-24
CAL5234 China Airlines 2 2026-05-23
CAL5233 China Airlines 2 2026-05-24
CAL5232 China Airlines 2 2026-05-25
TEST1234 - 1 2026-05-14
CAL6888 China Airlines 1 2026-05-28
CAL6887 China Airlines 1 2026-05-28
CAL6876 China Airlines 1 2026-05-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-30 CAL5265 SFO → ANC May 30, 12:45 UTCMay 30, 13:00 UTC15m
2026-05-30 CAL5265 SFO → ANC May 30, 03:20 UTCMay 30, 11:20 UTC8h 0m
2026-05-29 CAL5265 SFO → ANC May 29, 20:20 UTCMay 30, 01:55 UTC5h 35m
2026-05-29 CAL5266 ANC → DFW May 29, 10:20 UTCMay 29, 16:30 UTC6h 11m
2026-05-29 CAL5266 ANC → DFW May 29, 00:35 UTCMay 29, 08:50 UTC8h 15m
2026-05-28 CAL6888 TPE → TPE May 28, 13:35 UTCMay 28, 16:05 UTC2h 30m
2026-05-28 CAL6887 TPE → HAN May 28, 08:20 UTCMay 28, 10:40 UTC2h 20m
2026-05-26 CAL5231 ORD → ANC May 26, 19:34 UTCMay 26, 20:00 UTC25m
2026-05-26 CAL5231 ORD → ANC May 26, 10:14 UTCMay 26, 18:24 UTC8h 10m
2026-05-26 CAL5231 ORD → ANC May 26, 02:55 UTCMay 26, 08:45 UTC5h 50m
2026-05-25 CAL5232 ANC → ORD May 25, 19:20 UTCMay 26, 00:39 UTC5h 20m
2026-05-25 CAL5232 ANC → ORD May 25, 08:35 UTCMay 25, 17:35 UTC9h 0m
2026-05-25 CAL5828 HKG → TPE May 25, 02:15 UTCMay 25, 03:35 UTC1h 20m
2026-05-24 CAL5827 TPE → TPE May 24, 23:00 UTCMay 24, 23:10 UTC10m
2026-05-24 CAL5827 TPE → TPE May 24, 21:40 UTCMay 24, 21:45 UTC5m
2026-05-24 CAL5233 ANC → TPE May 24, 10:10 UTCMay 24, 19:50 UTC9h 40m
2026-05-24 CAL5233 ANC → TPE May 24, 02:35 UTCMay 24, 08:00 UTC5h 25m
2026-05-23 CAL5234 TPE → ANC May 23, 18:10 UTCMay 23, 23:35 UTC5h 25m
2026-05-23 CAL5234 TPE → ANC May 23, 08:35 UTCMay 23, 16:55 UTC8h 20m
2026-05-22 CAL5991 TPE → TPE May 22, 21:35 UTCMay 23, 03:10 UTC5h 34m
2026-05-22 CAL6876 SIN → TPE May 22, 08:45 UTCMay 22, 16:15 UTC7h 30m
2026-05-22 CAL6875 TPE → SIN May 22, 05:10 UTCMay 22, 05:20 UTC10m
2026-05-22 CAL6875 TPE → SIN May 22, 01:40 UTCMay 22, 02:40 UTC1h 0m
2026-05-21 CAL5265 SFO → ANC May 21, 14:00 UTCMay 21, 14:30 UTC30m
2026-05-21 CAL5265 SFO → ANC May 21, 04:40 UTCMay 21, 12:35 UTC7h 55m
2026-05-20 CAL5265 SFO → ANC May 20, 21:05 UTCMay 21, 03:20 UTC6h 15m
2026-05-20 CAL5266 ANC → DFW May 20, 12:45 UTCMay 20, 18:20 UTC5h 35m
2026-05-20 CAL5266 ANC → DFW May 20, 02:20 UTCMay 20, 10:45 UTC8h 26m
2026-05-19 CAL5928 SZX → TPE May 19, 21:30 UTCMay 19, 22:50 UTC1h 20m
2026-05-19 CAL5927 TPE → SZX May 19, 17:20 UTCMay 19, 17:40 UTC20m
2026-05-19 CAL5927 TPE → SZX May 19, 16:25 UTCMay 19, 16:50 UTC25m
2026-05-14 TEST1234 TPE → TPE May 14, 16:30 UTCMay 14, 16:45 UTC15m
2026-04-20 CAL5267 DFW → ANC Apr 20, 13:35 UTCApr 20, 23:15 UTC9h 40m
2026-04-20 CAL5267 DFW → ANC Apr 20, 05:10 UTCApr 20, 11:20 UTC6h 10m
2026-04-19 CAL5268 ANC → DFW Apr 19, 19:40 UTCApr 20, 01:05 UTC5h 25m
2026-04-19 CAL5268 ANC → DFW Apr 19, 11:55 UTCApr 19, 18:25 UTC6h 30m
2026-04-19 CAL5268 ANC → DFW Apr 19, 10:10 UTCApr 19, 10:25 UTC15m
2026-04-19 CAL5872 SIN → TPE Apr 19, 05:20 UTCApr 19, 06:25 UTC1h 5m
2026-04-18 CAL5871 TPE → SIN Apr 18, 17:05 UTCApr 18, 21:05 UTC4h 0m
2026-04-18 CAL6851 - Apr 18, 05:30 UTCApr 18, 05:50 UTC20m
2026-04-18 CAL6851 - Apr 18, 03:25 UTCApr 18, 03:55 UTC30m
2026-04-18 CAL6851 - Apr 18, 02:55 UTCApr 18, 14:20 UTC11h 25m
2026-04-17 CAL5898 PVG → TPE Apr 17, 23:40 UTCApr 18, 00:10 UTC30m
2026-04-17 CAL5897 - Apr 17, 17:45 UTCApr 17, 18:05 UTC20m
2026-04-17 CAL5225 ORD → ANC Apr 17, 14:35 UTCApr 17, 15:05 UTC29m
2026-04-17 CAL5225 ORD → ANC Apr 17, 11:40 UTCApr 17, 12:55 UTC1h 15m
2026-04-17 CAL5225 ORD → ANC Apr 17, 05:20 UTCApr 17, 06:55 UTC1h 35m
2026-04-17 CAL5225 ORD → ANC Apr 17, 03:20 UTCApr 17, 04:10 UTC50m
2026-04-17 CAL5225 ORD → ANC Apr 17, 02:50 UTCApr 17, 03:15 UTC25m
2026-04-16 CAL5225 ORD → ANC Apr 16, 23:20 UTCApr 17, 00:50 UTC1h 30m

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?
No active broadcast right now. Last signal was 1h ago.
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, CAL5226, CAL5225, CAL5265, CAL5268.