Apparatus

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sensors Mode-S transponder

A8B9B3

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N661UA · BOEING 767-300 · operated by UNITED AIRLINES INC

Hex
A8B9B3
Octal
52134663
Decimal
11,057,587
Country
US
Tail
N661UA
Type
B763
No current signal · last broadcast 23h ago
Flights observed
219
Distinct callsigns
20
Country
US
Last broadcast
23h ago

Last known position

Most recent position reported by Mode-S A8B9B3.

Country allocation

The ICAO 24-bit address A8B9B3 falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States 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
UAL135 - 13 2026-07-11
UAL55 United Airlines 12 2026-05-11
UAL134 - 11 2026-06-20
UAL904 United Airlines 10 2026-06-09
UAL3 - 10 2026-07-10
UAL958 - 9 2026-07-10
UAL54 United Airlines 9 2026-05-11
UAL147 - 9 2026-07-12
UAL964 United Airlines 8 2026-06-05
UAL957 United Airlines 8 2026-06-18
UAL306 United Airlines 8 2026-06-15
UAL965 United Airlines 7 2026-06-06
UAL940 United Airlines 7 2026-05-28
UAL934 - 7 2026-07-09
UAL920 United Airlines 7 2026-06-27
UAL956 - 6 2026-06-17
UAL941 United Airlines 6 2026-05-10
UAL921 United Airlines 6 2026-06-10
UAL272 - 5 2026-07-13
UAL12 - 5 2026-06-21

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 UAL272 EWR → NCE Jul 13, 00:05 UTCJul 13, 07:45 UTC7h 40m
2026-07-12 UAL147 LHR → EWR Jul 12, 11:35 UTCJul 12, 18:40 UTC7h 5m
2026-07-11 UAL16 EWR → LHR Jul 11, 22:20 UTCJul 12, 04:45 UTC6h 25m
2026-07-11 UAL135 ZRH → EWR Jul 11, 08:35 UTCJul 11, 17:15 UTC8h 40m
2026-07-10 UAL3 ORD → ZRH Jul 10, 21:32 UTCJul 11, 05:30 UTC7h 58m
2026-07-10 UAL3 ORD → ZRH Jul 10, 21:25 UTCJul 11, 05:31 UTC8h 5m
2026-07-10 UAL958 - Jul 10, 07:25 UTCJul 10, 08:40 UTC1h 15m
2026-07-10 UAL958 LHR → ORD Jul 10, 07:19 UTCJul 10, 15:31 UTC8h 12m
2026-07-09 UAL934 - Jul 9, 14:40 UTCJul 9, 21:05 UTC6h 25m
2026-07-08 UAL273 - Jul 8, 10:35 UTCJul 8, 12:05 UTC1h 30m
2026-07-08 UAL273 NCE → EWR Jul 8, 10:30 UTCJul 8, 18:56 UTC8h 26m
2026-07-08 UAL272 - Jul 8, 00:25 UTCJul 8, 01:55 UTC1h 30m
2026-07-08 UAL272 EWR → NCE Jul 8, 00:20 UTCJul 8, 07:47 UTC7h 27m
2026-07-06 UAL1149 EWR → SRQ Jul 6, 14:25 UTCJul 6, 19:20 UTC4h 55m
2026-07-06 UAL1558 EWR → SFO Jul 6, 00:10 UTCJul 6, 06:05 UTC5h 55m
2026-07-02 UAL3865 - Jul 2, 16:45 UTCJul 2, 18:15 UTC1h 30m
2026-06-30 UAL962 EWR → BER Jun 30, 21:43 UTCJun 30, 23:15 UTC1h 32m
2026-06-30 UAL962 EWR → BER Jun 30, 21:25 UTCJun 30, 23:20 UTC1h 55m
2026-06-29 UAL3934 - Jun 29, 12:05 UTCJun 29, 13:39 UTC1h 35m
2026-06-27 UAL920 ORD → LHR Jun 27, 00:29 UTCJun 27, 02:14 UTC1h 45m
2026-06-21 UAL12 ZRH → ORD Jun 21, 08:24 UTCJun 21, 17:08 UTC8h 44m
2026-06-21 UAL12 - Jun 21, 08:10 UTCJun 21, 16:44 UTC8h 35m
2026-06-20 UAL134 EWR → ZRH Jun 20, 22:39 UTCJun 21, 06:02 UTC7h 23m
2026-06-20 UAL134 EWR → ZRH Jun 20, 22:45 UTCJun 21, 06:04 UTC7h 20m
2026-06-20 UAL31 MUC → EWR Jun 20, 08:07 UTCJun 20, 16:29 UTC8h 22m
2026-06-20 UAL31 MUC → EWR Jun 20, 08:07 UTCJun 20, 16:18 UTC8h 11m
2026-06-19 UAL30 - Jun 19, 22:45 UTCJun 20, 04:44 UTC6h 0m
2026-06-18 UAL957 GVA → EWR Jun 18, 07:35 UTCJun 18, 08:45 UTC1h 10m
2026-06-18 UAL957 GVA → EWR Jun 18, 07:37 UTCJun 18, 15:49 UTC8h 12m
2026-06-17 UAL956 EWR → GVA Jun 17, 22:03 UTCJun 18, 04:56 UTC6h 53m
2026-06-17 UAL956 - Jun 17, 21:45 UTCJun 18, 04:45 UTC7h 0m
2026-06-17 UAL957 GVA → EWR Jun 17, 07:37 UTCJun 17, 15:19 UTC7h 42m
2026-06-17 UAL957 GVA → EWR Jun 17, 07:25 UTCJun 17, 15:20 UTC7h 55m
2026-06-16 UAL956 - Jun 16, 22:00 UTCJun 17, 04:55 UTC6h 55m
2026-06-16 UAL381 BDL → SMF Jun 16, 07:50 UTCJun 16, 17:15 UTC9h 25m
2026-06-15 UAL380 ORD → PDX Jun 15, 21:04 UTCJun 16, 05:05 UTC8h 0m
2026-06-15 UAL306 AUS → SFO Jun 15, 07:10 UTCJun 15, 16:19 UTC9h 10m
2026-06-15 UAL306 AUS → SFO Jun 15, 07:15 UTCJun 15, 16:18 UTC9h 3m
2026-06-14 UAL305 BOS → IAH Jun 14, 20:35 UTCJun 15, 04:04 UTC7h 30m
2026-06-14 UAL957 GVA → EWR Jun 14, 07:40 UTCJun 14, 08:45 UTC1h 5m
2026-06-14 UAL957 GVA → EWR Jun 14, 07:37 UTCJun 14, 15:46 UTC8h 9m
2026-06-13 UAL956 EWR → GVA Jun 13, 22:05 UTCJun 14, 05:10 UTC7h 5m
2026-06-13 UAL147 LHR → EWR Jun 13, 11:35 UTCJun 13, 19:00 UTC7h 25m
2026-06-13 UAL920 ORD → LHR Jun 13, 01:32 UTCJun 13, 08:35 UTC7h 3m
2026-06-13 UAL920 ORD → LHR Jun 13, 01:25 UTCJun 13, 08:35 UTC7h 9m
2026-06-12 UAL958 - Jun 12, 07:10 UTCJun 12, 09:40 UTC2h 30m
2026-06-12 UAL958 LHR → ORD Jun 12, 07:19 UTCJun 12, 15:08 UTC7h 49m
2026-06-11 UAL934 EWR → LHR Jun 11, 13:05 UTCJun 11, 19:30 UTC6h 25m
2026-06-10 UAL921 LHR → EWR Jun 10, 17:45 UTCJun 10, 18:45 UTC1h 0m
2026-06-10 UAL921 LHR → EWR Jun 10, 17:22 UTCJun 11, 01:17 UTC7h 55m

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 N661UA page for operator, model, and routing details .

Mode-S A8B9B3 frequently asked

What is Mode-S code A8B9B3?
A8B9B3 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N661UA.
Where is Mode-S A8B9B3 registered?
Mode-S code A8B9B3 is allocated to United States (US). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is A8B9B3 broadcasting right now?
No active broadcast right now. Last signal was 23h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A8B9B3, octal 52134663, decimal 11,057,587.
What flights does A8B9B3 operate?
Mode-S A8B9B3 has broadcast 20 distinct callsigns, including UAL135, UAL55, UAL134, UAL904, UAL3.