Apparatus

Try JFK, AAL1290, BAW, or N225AN.

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 1d ago
Flights observed
140
Distinct callsigns
20
Country
US
Last broadcast
1d 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
UAL55 United Airlines 12 2026-05-11
UAL54 United Airlines 9 2026-05-11
UAL135 United Airlines 9 2026-05-26
UAL134 United Airlines 8 2026-05-16
UAL940 United Airlines 7 2026-05-28
UAL904 United Airlines 7 2026-05-10
UAL147 United Airlines 7 2026-05-08
UAL941 United Airlines 6 2026-05-10
UAL306 United Airlines 6 2026-05-27
UAL3 United Airlines 6 2026-05-25
UAL965 United Airlines 5 2026-05-05
UAL964 United Airlines 5 2026-05-04
UAL958 United Airlines 5 2026-05-25
UAL934 United Airlines 5 2026-05-24
UAL921 United Airlines 4 2026-05-23
UAL920 United Airlines 4 2026-04-29
UAL905 United Airlines 4 2026-04-15
UAL908 United Airlines 3 2026-04-28
UAL305 United Airlines 3 2026-05-26
UAL15 United Airlines 3 2026-05-12

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-28 UAL928 LHR → ORD May 28, 13:40 UTCMay 28, 21:25 UTC7h 45m
2026-05-28 UAL940 EWR → LHR May 28, 01:30 UTCMay 28, 08:10 UTC6h 40m
2026-05-27 UAL306 AUS → SFO May 27, 07:50 UTCMay 27, 17:05 UTC9h 15m
2026-05-27 UAL306 AUS → SFO May 27, 07:35 UTCMay 27, 16:47 UTC9h 12m
2026-05-26 UAL305 BOS → IAH May 26, 20:40 UTCMay 27, 04:45 UTC8h 5m
2026-05-26 UAL135 ZRH → EWR May 26, 08:34 UTCMay 26, 17:09 UTC8h 35m
2026-05-25 UAL3 LAX → HNL May 25, 21:32 UTCMay 26, 05:25 UTC7h 53m
2026-05-25 UAL3 LAX → HNL May 25, 21:19 UTCMay 26, 05:30 UTC8h 10m
2026-05-25 UAL958 ORD → LHR May 25, 07:10 UTCMay 25, 15:40 UTC8h 30m
2026-05-24 UAL934 EWR → LHR May 24, 12:40 UTCMay 24, 19:15 UTC6h 35m
2026-05-23 UAL921 LHR → EWR May 23, 17:25 UTCMay 24, 00:50 UTC7h 25m
2026-05-23 UAL921 LHR → EWR May 23, 17:22 UTCMay 24, 00:50 UTC7h 28m
2026-05-22 UAL16 EWR → LHR May 22, 21:58 UTCMay 23, 04:09 UTC6h 11m
2026-05-22 UAL16 EWR → LHR May 22, 21:55 UTCMay 23, 04:20 UTC6h 25m
2026-05-22 UAL306 AUS → SFO May 22, 08:05 UTCMay 22, 16:50 UTC8h 45m
2026-05-21 UAL305 BOS → IAH May 21, 21:05 UTCMay 22, 04:15 UTC7h 10m
2026-05-20 UAL921 LHR → EWR May 20, 21:10 UTCMay 21, 05:00 UTC7h 50m
2026-05-20 UAL921 LHR → EWR May 20, 21:12 UTCMay 21, 04:59 UTC7h 47m
2026-05-20 UAL934 EWR → LHR May 20, 12:50 UTCMay 20, 19:35 UTC6h 45m
2026-05-19 UAL381 BDL → SMF May 19, 08:10 UTCMay 19, 10:45 UTC2h 35m
2026-05-19 UAL381 BDL → SMF May 19, 08:03 UTCMay 19, 17:46 UTC9h 43m
2026-05-18 UAL380 ORD → PDX May 18, 20:45 UTCMay 19, 05:00 UTC8h 15m
2026-05-18 UAL306 AUS → SFO May 18, 15:30 UTCMay 18, 17:05 UTC1h 35m
2026-05-18 UAL306 AUS → SFO May 18, 08:15 UTCMay 18, 15:25 UTC7h 10m
2026-05-18 UAL306 AUS → SFO May 18, 08:15 UTCMay 18, 17:01 UTC8h 46m
2026-05-17 UAL305 BOS → IAH May 17, 20:30 UTCMay 18, 04:15 UTC7h 45m
2026-05-17 UAL135 ZRH → EWR May 17, 08:30 UTCMay 17, 10:55 UTC2h 25m
2026-05-17 UAL135 ZRH → EWR May 17, 08:20 UTCMay 17, 17:06 UTC8h 46m
2026-05-16 UAL134 EWR → ZRH May 16, 22:30 UTCMay 17, 05:50 UTC7h 20m
2026-05-16 UAL135 ZRH → EWR May 16, 08:36 UTCMay 16, 17:01 UTC8h 25m
2026-05-15 UAL134 EWR → ZRH May 15, 22:25 UTCMay 16, 05:30 UTC7h 5m
2026-05-15 UAL135 ZRH → EWR May 15, 08:30 UTCMay 15, 17:04 UTC8h 34m
2026-05-15 UAL135 ZRH → EWR May 15, 08:25 UTCMay 15, 17:00 UTC8h 34m
2026-05-14 UAL3 LAX → HNL May 14, 21:33 UTCMay 15, 05:31 UTC7h 58m
2026-05-14 UAL3 LAX → HNL May 14, 21:20 UTCMay 15, 05:35 UTC8h 15m
2026-05-14 UAL958 ORD → LHR May 14, 07:10 UTCMay 14, 15:05 UTC7h 55m
2026-05-13 UAL934 EWR → LHR May 13, 12:52 UTCMay 13, 19:22 UTC6h 30m
2026-05-13 UAL934 EWR → LHR May 13, 12:35 UTCMay 13, 19:20 UTC6h 45m
2026-05-12 UAL15 LHR → EWR May 12, 14:45 UTCMay 12, 22:20 UTC7h 35m
2026-05-12 UAL15 LHR → EWR May 12, 14:44 UTCMay 12, 22:13 UTC7h 29m
2026-05-12 UAL146 EWR → LHR May 12, 02:45 UTCMay 12, 09:00 UTC6h 15m
2026-05-11 UAL55 CDG → EWR May 11, 12:00 UTCMay 11, 19:45 UTC7h 45m
2026-05-11 UAL54 EWR → CDG May 11, 01:34 UTCMay 11, 08:16 UTC6h 42m
2026-05-11 UAL54 EWR → CDG May 11, 01:25 UTCMay 11, 08:25 UTC7h 0m
2026-05-10 UAL941 LHR → EWR May 10, 15:35 UTCMay 10, 16:44 UTC1h 10m
2026-05-10 UAL941 LHR → EWR May 10, 15:24 UTCMay 10, 23:02 UTC7h 38m
2026-05-10 UAL941 LHR → EWR May 10, 15:24 UTCMay 10, 22:52 UTC7h 28m
2026-05-10 UAL904 EWR → LHR May 10, 00:45 UTCMay 10, 07:40 UTC6h 55m
2026-05-10 UAL904 EWR → LHR May 10, 00:35 UTCMay 10, 07:22 UTC6h 47m
2026-05-09 UAL55 CDG → EWR May 9, 11:25 UTCMay 9, 19:10 UTC7h 45m

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 1d 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 UAL55, UAL54, UAL135, UAL134, UAL940.