Apparatus

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sensors Mode-S transponder

A8F77C

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N677UA · BOEING 767-300 · operated by UNITED AIRLINES INC

Hex
A8F77C
Octal
52173574
Decimal
11,073,404
Country
US
Tail
N677UA
Type
B763
Broadcasting now · callsign UAL146 · 34,800 ft
Flights observed
255
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:10 UTC

Current position

A8F77C is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A8F77C 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
UAL12 United Airlines 19 2026-07-22
UAL3 United Airlines 15 2026-06-29
UAL134 United Airlines 15 2026-07-21
UAL958 - 13 2026-07-02
UAL135 - 13 2026-06-30
UAL904 United Airlines 12 2026-06-12
UAL921 - 11 2026-07-19
UAL929 - 10 2026-07-14
UAL147 United Airlines 10 2026-07-21
UAL941 - 9 2026-07-06
UAL16 United Airlines 9 2026-07-17
UAL934 - 7 2026-07-23
UAL920 - 7 2026-07-21
UAL273 - 7 2026-07-10
UAL964 United Airlines 6 2026-07-26
UAL938 - 6 2026-06-26
UAL928 United Airlines 6 2026-06-25
UAL17 - 5 2026-07-15
UAL15 United Airlines 5 2026-07-24
UAL146 United Airlines 5 2026-04-25

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL3016 OGG → SFO Jul 26, 10:55 UTCJul 26, 20:10 UTC9h 15m
2026-07-26 UAL964 EWR → NAP Jul 26, 00:23 UTCJul 26, 08:19 UTC7h 56m
2026-07-26 UAL964 EWR → NAP Jul 26, 00:20 UTCJul 26, 08:05 UTC7h 46m
2026-07-24 UAL15 LHR → EWR Jul 24, 14:54 UTCJul 24, 22:07 UTC7h 13m
2026-07-23 UAL934 EWR → LHR Jul 23, 13:00 UTCJul 23, 19:10 UTC6h 10m
2026-07-22 UAL12 HNL → LAX Jul 22, 13:20 UTCJul 22, 21:20 UTC8h 0m
2026-07-21 UAL134 EWR → ZRH Jul 21, 23:55 UTCJul 22, 05:25 UTC5h 30m
2026-07-21 UAL147 LHR → EWR Jul 21, 11:25 UTCJul 21, 18:45 UTC7h 20m
2026-07-21 UAL147 LHR → EWR Jul 21, 11:25 UTCJul 21, 18:46 UTC7h 21m
2026-07-21 UAL920 ORD → LHR Jul 21, 00:05 UTCJul 21, 07:25 UTC7h 20m
2026-07-20 UAL12 HNL → LAX Jul 20, 10:45 UTCJul 20, 13:00 UTC2h 15m
2026-07-20 UAL12 HNL → LAX Jul 20, 10:44 UTCJul 20, 19:40 UTC8h 56m
2026-07-20 UAL134 EWR → ZRH Jul 20, 00:55 UTCJul 20, 08:10 UTC7h 15m
2026-07-19 UAL921 ORD → EWR Jul 19, 12:25 UTCJul 19, 13:55 UTC1h 30m
2026-07-19 UAL921 ORD → EWR Jul 19, 12:12 UTCJul 19, 13:52 UTC1h 40m
2026-07-18 UAL921 - Jul 18, 17:25 UTCJul 19, 02:05 UTC8h 40m
2026-07-17 UAL16 EWR → LHR Jul 17, 22:10 UTCJul 18, 04:40 UTC6h 31m
2026-07-17 UAL31 - Jul 17, 08:15 UTCJul 17, 16:40 UTC8h 25m
2026-07-16 UAL30 - Jul 16, 21:10 UTCJul 17, 04:39 UTC7h 30m
2026-07-16 UAL31 MUC → EWR Jul 16, 08:00 UTCJul 16, 16:25 UTC8h 25m
2026-07-16 UAL31 MUC → EWR Jul 16, 08:07 UTCJul 16, 16:25 UTC8h 18m
2026-07-15 UAL30 EWR → MUC Jul 15, 21:45 UTCJul 16, 05:45 UTC8h 0m
2026-07-15 UAL17 - Jul 15, 10:10 UTCJul 15, 17:25 UTC7h 15m
2026-07-14 UAL929 ORD → LHR Jul 14, 22:35 UTCJul 15, 06:10 UTC7h 34m
2026-07-14 UAL929 ORD → LHR Jul 14, 22:03 UTCJul 15, 06:04 UTC8h 1m
2026-07-14 UAL12 ZRH → ORD Jul 14, 08:10 UTCJul 14, 17:10 UTC9h 0m
2026-07-13 UAL134 EWR → ZRH Jul 13, 22:40 UTCJul 14, 06:10 UTC7h 30m
2026-07-10 UAL273 NCE → EWR Jul 10, 10:55 UTCJul 10, 19:35 UTC8h 40m
2026-07-10 UAL272 - Jul 10, 01:20 UTCJul 10, 08:45 UTC7h 25m
2026-07-08 UAL509 DEN → SFO Jul 8, 16:20 UTCJul 8, 17:00 UTC40m
2026-07-08 UAL509 FCO → EWR Jul 8, 15:57 UTCJul 9, 00:46 UTC8h 49m
2026-07-08 UAL509 FCO → EWR Jul 8, 15:57 UTCJul 9, 00:42 UTC8h 45m
2026-07-08 UAL510 - Jul 8, 06:05 UTCJul 8, 14:05 UTC8h 0m
2026-07-07 UAL967 - Jul 7, 13:20 UTCJul 7, 22:30 UTC9h 10m
2026-07-07 UAL966 EWR → NAP Jul 7, 02:36 UTCJul 7, 10:58 UTC8h 22m
2026-07-07 UAL966 - Jul 7, 02:50 UTCJul 7, 10:55 UTC8h 5m
2026-07-06 UAL941 - Jul 6, 16:10 UTCJul 6, 17:00 UTC50m
2026-07-06 UAL941 LHR → EWR Jul 6, 15:39 UTCJul 6, 23:35 UTC7h 56m
2026-07-06 UAL941 LHR → EWR Jul 6, 15:39 UTCJul 6, 23:24 UTC7h 45m
2026-07-06 UAL16 EWR → LHR Jul 6, 06:43 UTCJul 6, 13:02 UTC6h 19m
2026-07-06 UAL16 EWR → LHR Jul 6, 06:45 UTCJul 6, 13:10 UTC6h 25m
2026-07-05 UAL3028 ZRH → EWR Jul 5, 08:40 UTCJul 5, 17:20 UTC8h 40m
2026-07-04 UAL134 EWR → ZRH Jul 4, 06:34 UTCJul 4, 13:36 UTC7h 2m
2026-07-04 UAL134 - Jul 4, 06:35 UTCJul 4, 08:15 UTC1h 40m
2026-07-03 UAL147 - Jul 3, 11:25 UTCJul 3, 18:55 UTC7h 30m
2026-07-03 UAL920 ORD → LHR Jul 3, 00:20 UTCJul 3, 07:00 UTC6h 40m
2026-07-03 UAL920 ORD → LHR Jul 3, 00:07 UTCJul 3, 07:10 UTC7h 3m
2026-07-02 UAL958 - Jul 2, 07:25 UTCJul 2, 08:35 UTC1h 10m
2026-07-02 UAL958 LHR → ORD Jul 2, 07:19 UTCJul 2, 15:48 UTC8h 29m
2026-07-01 UAL16 - Jul 1, 22:05 UTCJul 2, 04:35 UTC6h 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 N677UA page for operator, model, and routing details .

Mode-S A8F77C frequently asked

What is Mode-S code A8F77C?
A8F77C is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N677UA.
Where is Mode-S A8F77C registered?
Mode-S code A8F77C 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 A8F77C broadcasting right now?
Yes. Mode-S A8F77C is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A8F77C, octal 52173574, decimal 11,073,404.
What flights does A8F77C operate?
Mode-S A8F77C has broadcast 20 distinct callsigns, including UAL12, UAL3, UAL134, UAL958, UAL135.