sensors Mode-S transponder

8991B4

ICAO 24-bit transponder address · allocated to Taiwan

Currently assigned to B-18306 · AIRBUS A-330-300

Hex
8991B4
Octal
42310664
Decimal
9,015,732
Country
TW
Tail
B-18306
Type
A333
No current signal · last broadcast 11h ago
Flights observed
154
Distinct callsigns
20
Country
TW
Last broadcast
11h ago

Last known position

Most recent position reported by Mode-S 8991B4.

Country allocation

The ICAO 24-bit address 8991B4 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
CAL117 China Airlines 15 2026-05-25
CAL116 China Airlines 11 2026-05-25
CAL157 China Airlines 10 2026-05-25
CAL791 China Airlines 7 2026-05-18
CAL792 China Airlines 6 2026-05-18
CAL156 China Airlines 6 2026-05-25
CAL130 China Airlines 6 2026-04-28
CAL836 China Airlines 5 2026-05-29
CAL131 China Airlines 5 2026-04-28
CAL919 China Airlines 4 2026-05-15
CAL835 China Airlines 4 2026-05-29
CAL702 China Airlines 4 2026-05-14
CAL701 China Airlines 4 2026-05-14
CAL601 China Airlines 4 2026-05-29
CAL521 China Airlines 4 2026-05-14
CAL173 China Airlines 4 2026-04-27
CAL923 China Airlines 3 2026-05-28
CAL704 China Airlines 3 2026-05-08
CAL703 China Airlines 3 2026-05-08
CAL155 China Airlines 3 2026-05-26

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-29 CAL836 BKK → TPE May 29, 10:55 UTCMay 29, 14:10 UTC3h 15m
2026-05-29 CAL835 TPE → BKK May 29, 06:00 UTCMay 29, 09:20 UTC3h 20m
2026-05-29 CAL602 HKG → TPE May 29, 02:20 UTCMay 29, 03:45 UTC1h 25m
2026-05-29 CAL601 TPE → HKG May 29, 00:35 UTCMay 29, 00:50 UTC15m
2026-05-28 CAL601 TPE → HKG May 28, 23:30 UTCMay 29, 00:00 UTC30m
2026-05-28 CAL924 HKG → TPE May 28, 13:30 UTCMay 28, 15:00 UTC1h 30m
2026-05-28 CAL923 TPE → HKG May 28, 10:45 UTCMay 28, 11:55 UTC1h 10m
2026-05-27 CAL101 NRT → TPE May 27, 08:50 UTCMay 27, 09:25 UTC35m
2026-05-27 CAL101 NRT → TPE May 27, 06:20 UTCMay 27, 07:30 UTC1h 11m
2026-05-27 CAL100 TPE → NRT May 27, 01:39 UTCMay 27, 04:30 UTC2h 50m
2026-05-26 CAL155 NGO → TPE May 26, 03:50 UTCMay 26, 06:14 UTC2h 25m
2026-05-25 CAL154 TPE → NGO May 25, 23:40 UTCMay 26, 02:00 UTC2h 20m
2026-05-25 CAL117 FUK → TPE May 25, 13:55 UTCMay 25, 14:25 UTC30m
2026-05-25 CAL116 TPE → FUK May 25, 09:05 UTCMay 25, 09:30 UTC25m
2026-05-25 CAL157 KIX → TPE May 25, 06:40 UTCMay 25, 07:05 UTC25m
2026-05-25 CAL157 KIX → TPE May 25, 04:45 UTCMay 25, 05:15 UTC30m
2026-05-25 CAL156 TPE → KIX May 25, 02:15 UTCMay 25, 02:55 UTC40m
2026-05-22 CAL832 BKK → TPE May 22, 06:45 UTCMay 22, 10:10 UTC3h 25m
2026-05-22 CAL831 TPE → BKK May 22, 01:55 UTCMay 22, 05:10 UTC3h 15m
2026-05-21 CAL155 NGO → TPE May 21, 06:20 UTCMay 21, 06:50 UTC30m
2026-05-21 CAL155 NGO → TPE May 21, 04:10 UTCMay 21, 04:50 UTC40m
2026-05-20 CAL154 TPE → NGO May 20, 23:45 UTCMay 21, 02:00 UTC2h 15m
2026-05-20 CAL157 KIX → TPE May 20, 04:30 UTCMay 20, 06:50 UTC2h 21m
2026-05-20 CAL156 TPE → KIX May 20, 00:40 UTCMay 20, 02:55 UTC2h 15m
2026-05-19 CAL836 BKK → TPE May 19, 10:40 UTCMay 19, 14:20 UTC3h 40m
2026-05-19 CAL835 TPE → BKK May 19, 05:50 UTCMay 19, 09:05 UTC3h 15m
2026-05-18 CAL117 FUK → TPE May 18, 13:35 UTCMay 18, 14:00 UTC25m
2026-05-18 CAL117 FUK → TPE May 18, 12:10 UTCMay 18, 12:20 UTC10m
2026-05-18 CAL116 TPE → FUK May 18, 08:50 UTCMay 18, 09:10 UTC20m
2026-05-18 CAL792 HAN → TPE May 18, 06:35 UTCMay 18, 07:00 UTC25m
2026-05-18 CAL791 TPE → HAN May 18, 00:40 UTCMay 18, 06:01 UTC5h 20m
2026-05-17 CAL117 FUK → TPE May 17, 13:40 UTCMay 17, 14:10 UTC30m
2026-05-17 CAL116 TPE → FUK May 17, 09:10 UTCMay 17, 09:30 UTC20m
2026-05-17 CAL791 TPE → HAN May 17, 00:55 UTCMay 17, 07:25 UTC6h 30m
2026-05-16 CAL117 FUK → TPE May 16, 13:55 UTCMay 16, 14:25 UTC30m
2026-05-16 CAL117 FUK → TPE May 16, 12:31 UTCMay 16, 12:40 UTC10m
2026-05-16 CAL116 TPE → FUK May 16, 09:25 UTCMay 16, 09:35 UTC10m
2026-05-16 CAL792 HAN → TPE May 16, 01:15 UTCMay 16, 07:51 UTC6h 36m
2026-05-15 CAL920 HKG → TPE May 15, 13:35 UTCMay 15, 14:55 UTC1h 19m
2026-05-15 CAL919 TPE → HKG May 15, 11:30 UTCMay 15, 11:50 UTC20m
2026-05-15 CAL919 TPE → HKG May 15, 10:25 UTCMay 15, 10:55 UTC30m
2026-05-15 CAL834 BKK → TPE May 15, 04:10 UTCMay 15, 07:25 UTC3h 15m
2026-05-14 CAL833 TPE → BKK May 14, 23:15 UTCMay 15, 02:35 UTC3h 20m
2026-05-14 CAL522 CAN → TPE May 14, 10:55 UTCMay 14, 12:10 UTC1h 15m
2026-05-14 CAL521 TPE → CAN May 14, 07:40 UTCMay 14, 08:00 UTC20m
2026-05-14 CAL521 TPE → CAN May 14, 06:35 UTCMay 14, 07:05 UTC30m
2026-05-14 CAL702 MNL → TPE May 14, 03:05 UTCMay 14, 04:55 UTC1h 50m
2026-05-14 CAL701 TPE → MNL May 14, 00:05 UTCMay 14, 01:45 UTC1h 40m
2026-05-13 CAL117 FUK → TPE May 13, 14:00 UTCMay 13, 14:30 UTC30m
2026-05-13 CAL116 TPE → FUK May 13, 09:05 UTCMay 13, 09:30 UTC25m

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-18306 page for operator, model, and routing details .

Mode-S 8991B4 frequently asked

What is Mode-S code 8991B4?
8991B4 is an ICAO 24-bit transponder address. Allocated to Taiwan. Assigned to B-18306.
Where is Mode-S 8991B4 registered?
Mode-S code 8991B4 is allocated to Taiwan (TW). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 8991B4 broadcasting right now?
No active broadcast right now. Last signal was 11h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 8991B4, octal 42310664, decimal 9,015,732.
What flights does 8991B4 operate?
Mode-S 8991B4 has broadcast 20 distinct callsigns, including CAL117, CAL116, CAL157, CAL791, CAL792.