Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A31A56

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N29977 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC

Hex
A31A56
Octal
50615126
Decimal
10,689,110
Country
US
Tail
N29977
Type
B789
No current signal · last broadcast 2h ago
Flights observed
173
Distinct callsigns
20
Country
US
Last broadcast
2h ago

Last known position

Most recent position reported by Mode-S A31A56.

Country allocation

The ICAO 24-bit address A31A56 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
UAL805 - 9 2026-07-13
UAL839 United Airlines 8 2026-06-13
UAL821 - 8 2026-06-12
UAL152 United Airlines 8 2026-06-30
UAL188 - 7 2026-07-10
UAL153 United Airlines 7 2026-07-01
UAL820 - 6 2026-06-12
UAL2692 - 6 2026-07-02
UAL122 - 6 2026-07-11
UAL842 United Airlines 5 2026-06-14
UAL83 United Airlines 5 2026-07-07
UAL806 - 5 2026-07-14
UAL123 - 5 2026-07-12
UAL263 - 4 2026-06-26
UAL262 - 4 2026-06-26
UAL2096 United Airlines 4 2026-07-04
UAL199 United Airlines 4 2026-04-28
UAL187 - 4 2026-07-05
UAL82 - 3 2026-07-07
UAL62 - 3 2026-06-18

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 UAL806 - Jul 14, 03:05 UTCJul 14, 04:40 UTC1h 35m
2026-07-13 UAL805 SFO → ICN Jul 13, 07:40 UTCJul 13, 19:07 UTC11h 27m
2026-07-13 UAL805 SFO → ICN Jul 13, 07:55 UTCJul 13, 19:10 UTC11h 15m
2026-07-12 UAL1227 - Jul 12, 18:20 UTCJul 12, 23:10 UTC4h 50m
2026-07-12 UAL123 LHR → EWR Jul 12, 07:15 UTCJul 12, 14:10 UTC6h 55m
2026-07-11 UAL122 EWR → LHR Jul 11, 14:10 UTCJul 11, 20:20 UTC6h 10m
2026-07-11 UAL187D - Jul 11, 10:10 UTCJul 11, 10:55 UTC45m
2026-07-10 UAL187D - Jul 10, 20:15 UTCJul 11, 04:05 UTC7h 50m
2026-07-10 UAL187D JNB → EWR Jul 10, 20:19 UTCJul 11, 10:57 UTC14h 38m
2026-07-10 UAL188 EWR → JNB Jul 10, 02:29 UTCJul 10, 16:18 UTC13h 49m
2026-07-10 UAL188 - Jul 10, 02:30 UTCJul 10, 03:05 UTC35m
2026-07-09 UAL123 LHR → EWR Jul 9, 07:02 UTCJul 9, 13:57 UTC6h 55m
2026-07-09 UAL123 LHR → EWR Jul 9, 06:55 UTCJul 9, 13:55 UTC7h 0m
2026-07-08 UAL122 EWR → LHR Jul 8, 13:50 UTCJul 8, 20:05 UTC6h 15m
2026-07-07 UAL83 DEL → EWR Jul 7, 18:35 UTCJul 8, 10:25 UTC15h 50m
2026-07-07 UAL82 - Jul 7, 02:20 UTCJul 7, 16:10 UTC13h 50m
2026-07-05 UAL187 - Jul 5, 21:30 UTCJul 6, 12:25 UTC14h 55m
2026-07-05 UAL188 EWR → JNB Jul 5, 05:25 UTCJul 5, 19:20 UTC13h 55m
2026-07-04 UAL2096 LAX → EWR Jul 4, 15:40 UTCJul 4, 20:20 UTC4h 40m
2026-07-04 UAL353 - Jul 4, 02:05 UTCJul 4, 07:00 UTC4h 55m
2026-07-02 UAL1855 - Jul 2, 20:50 UTCJul 3, 01:25 UTC4h 35m
2026-07-02 UAL2692 EWR → LAX Jul 2, 14:04 UTCJul 2, 18:33 UTC4h 29m
2026-07-02 UAL2692 - Jul 2, 13:40 UTCJul 2, 18:40 UTC5h 0m
2026-07-02 UAL1855 - Jul 2, 02:10 UTCJul 2, 06:30 UTC4h 20m
2026-07-02 UAL1855 LAX → EWR Jul 2, 01:51 UTCJul 2, 06:27 UTC4h 36m
2026-07-01 UAL153 HKG → LAX Jul 1, 05:05 UTCJul 1, 17:35 UTC12h 30m
2026-07-01 UAL153 HKG → LAX Jul 1, 02:15 UTCJul 1, 02:20 UTC5m
2026-06-30 UAL152 LAX → HKG Jun 30, 13:25 UTCJun 30, 13:40 UTC15m
2026-06-29 UAL152 LAX → HKG Jun 29, 20:35 UTCJun 30, 10:35 UTC14h 1m
2026-06-29 UAL33 - Jun 29, 09:00 UTCJun 29, 18:14 UTC9h 15m
2026-06-28 UAL143 DEN → NRT Jun 28, 18:04 UTCJun 29, 05:14 UTC11h 10m
2026-06-28 UAL143 DEN → NRT Jun 28, 18:05 UTCJun 29, 05:04 UTC11h 0m
2026-06-27 UAL761 MUC → DEN Jun 27, 14:39 UTCJun 28, 00:55 UTC10h 15m
2026-06-27 UAL760 DEN → MUC Jun 27, 02:59 UTCJun 27, 12:15 UTC9h 15m
2026-06-26 UAL263 - Jun 26, 14:29 UTCJun 26, 23:25 UTC8h 55m
2026-06-26 UAL262 DEN → LHR Jun 26, 02:54 UTCJun 26, 11:24 UTC8h 30m
2026-06-25 UAL761 MUC → DEN Jun 25, 14:39 UTCJun 26, 00:24 UTC9h 45m
2026-06-25 UAL760 - Jun 25, 02:45 UTCJun 25, 11:59 UTC9h 15m
2026-06-24 UAL263 - Jun 24, 14:24 UTCJun 24, 16:50 UTC2h 25m
2026-06-24 UAL263 LHR → DEN Jun 24, 14:14 UTCJun 24, 23:10 UTC8h 56m
2026-06-24 UAL262 DEN → LHR Jun 24, 02:40 UTCJun 24, 11:09 UTC8h 30m
2026-06-23 UAL263 - Jun 23, 14:10 UTCJun 23, 23:05 UTC8h 55m
2026-06-23 UAL262 DEN → LHR Jun 23, 02:45 UTCJun 23, 10:42 UTC7h 57m
2026-06-23 UAL262 DEN → LHR Jun 23, 02:40 UTCJun 23, 10:59 UTC8h 20m
2026-06-22 UAL178 KIX → GUM Jun 22, 12:49 UTCJun 22, 23:45 UTC10h 55m
2026-06-22 UAL177 DEN → FCO Jun 22, 00:20 UTCJun 22, 10:19 UTC10h 0m
2026-06-21 UAL26 - Jun 21, 11:00 UTCJun 21, 20:14 UTC9h 15m
2026-06-20 UAL27 DEN → LHR Jun 20, 23:59 UTCJun 21, 08:25 UTC8h 25m
2026-06-20 UAL142 NRT → DEN Jun 20, 07:59 UTCJun 20, 17:59 UTC10h 0m
2026-06-19 UAL7 - Jun 19, 16:49 UTCJun 20, 05:24 UTC12h 35m

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 N29977 page for operator, model, and routing details .

Mode-S A31A56 frequently asked

What is Mode-S code A31A56?
A31A56 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N29977.
Where is Mode-S A31A56 registered?
Mode-S code A31A56 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 A31A56 broadcasting right now?
No active broadcast right now. Last signal was 2h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A31A56, octal 50615126, decimal 10,689,110.
What flights does A31A56 operate?
Mode-S A31A56 has broadcast 20 distinct callsigns, including UAL805, UAL839, UAL821, UAL152, UAL188.