Apparatus

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sensors Mode-S transponder

A31A73

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N29981 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC

Hex
A31A73
Octal
50615163
Decimal
10,689,139
Country
US
Tail
N29981
Type
B789
No current signal · last broadcast Jul 26, 20:10 UTC
Flights observed
201
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:10 UTC

Last known position

Most recent position reported by Mode-S A31A73.

Country allocation

The ICAO 24-bit address A31A73 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
UAL152 United Airlines 22 2026-07-01
UAL153 United Airlines 21 2026-07-02
UAL198 United Airlines 10 2026-06-07
UAL842 - 7 2026-06-30
UAL199 United Airlines 7 2026-06-07
UAL187 United Airlines 7 2026-07-17
UAL82 United Airlines 6 2026-07-19
UAL1227 United Airlines 6 2026-07-20
UAL61 United Airlines 5 2026-07-23
UAL2303 - 5 2026-06-17
UAL188 - 5 2026-07-17
UAL1855 - 5 2026-07-03
UAL123 - 5 2026-07-14
UAL923 - 4 2026-06-27
UAL863 - 4 2026-06-29
UAL83 United Airlines 4 2026-07-19
UAL713 - 4 2026-07-16
UAL60 United Airlines 4 2026-07-22
UAL33 - 4 2026-06-23
UAL32 - 4 2026-06-19

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL29 SFO → SIN Jul 26, 19:40 UTCJul 26, 20:10 UTC30m
2026-07-26 UAL806 ICN → SFO Jul 26, 02:45 UTCJul 26, 13:00 UTC10h 16m
2026-07-25 UAL805 SFO → ICN Jul 25, 07:37 UTCJul 25, 19:01 UTC11h 24m
2026-07-25 UAL805 SFO → ICN Jul 25, 07:40 UTCJul 25, 19:10 UTC11h 30m
2026-07-24 UAL1757 PIT → DEN Jul 24, 23:25 UTCJul 25, 04:50 UTC5h 25m
2026-07-24 UAL1849 MCO → EWR Jul 24, 17:35 UTCJul 24, 21:45 UTC4h 10m
2026-07-23 UAL61 BRU → IAH Jul 23, 02:50 UTCJul 23, 04:35 UTC1h 45m
2026-07-23 UAL61 BRU → IAH Jul 23, 02:39 UTCJul 23, 16:15 UTC13h 36m
2026-07-22 UAL60 SFO → MEL Jul 22, 20:25 UTCJul 22, 23:00 UTC2h 35m
2026-07-21 UAL1757 PIT → DEN Jul 21, 22:20 UTCJul 22, 03:20 UTC5h 0m
2026-07-21 UAL1849 MCO → EWR Jul 21, 15:45 UTCJul 21, 20:45 UTC5h 0m
2026-07-20 UAL1227 PHX → IAD Jul 20, 17:50 UTCJul 20, 22:50 UTC5h 0m
2026-07-19 UAL83 DEL → EWR Jul 19, 21:25 UTCJul 20, 12:55 UTC15h 30m
2026-07-19 UAL82 EWR → DEL Jul 19, 04:14 UTCJul 19, 18:40 UTC14h 26m
2026-07-19 UAL82 EWR → DEL Jul 19, 04:50 UTCJul 19, 14:55 UTC10h 5m
2026-07-17 UAL187 JNB → EWR Jul 17, 20:19 UTCJul 18, 10:33 UTC14h 14m
2026-07-17 UAL187 JNB → EWR Jul 17, 20:00 UTCJul 18, 10:35 UTC14h 36m
2026-07-17 UAL188 EWR → JNB Jul 17, 01:54 UTCJul 17, 16:26 UTC14h 32m
2026-07-17 UAL188 EWR → JNB Jul 17, 02:15 UTCJul 17, 16:19 UTC14h 5m
2026-07-16 UAL713 SFO → EWR Jul 16, 18:05 UTCJul 16, 22:45 UTC4h 40m
2026-07-16 UAL114 PPT → SFO Jul 16, 07:30 UTCJul 16, 14:49 UTC7h 19m
2026-07-16 UAL114 - Jul 16, 07:05 UTCJul 16, 14:55 UTC7h 50m
2026-07-15 UAL115 SFO → PPT Jul 15, 20:55 UTCJul 16, 04:55 UTC8h 0m
2026-07-14 UAL1227 EWR → SFO Jul 14, 18:00 UTCJul 14, 23:25 UTC5h 24m
2026-07-14 UAL123 - Jul 14, 07:25 UTCJul 14, 08:35 UTC1h 10m
2026-07-14 UAL123 LHR → EWR Jul 14, 07:12 UTCJul 14, 14:00 UTC6h 48m
2026-07-14 UAL123 LHR → EWR Jul 14, 07:12 UTCJul 14, 14:00 UTC6h 48m
2026-07-13 UAL122 EWR → LHR Jul 13, 14:19 UTCJul 13, 20:19 UTC6h 0m
2026-07-13 UAL122 - Jul 13, 14:00 UTCJul 13, 20:20 UTC6h 20m
2026-07-12 UAL83 - Jul 12, 18:45 UTCJul 13, 09:55 UTC15h 10m
2026-07-12 UAL82 - Jul 12, 02:45 UTCJul 12, 04:15 UTC1h 30m
2026-07-12 UAL82 EWR → DEL Jul 12, 02:19 UTCJul 12, 16:32 UTC14h 13m
2026-07-11 UAL83 FRA → EWR Jul 11, 07:15 UTCJul 11, 15:10 UTC7h 55m
2026-07-10 UAL83 - Jul 10, 21:15 UTCJul 11, 05:31 UTC8h 15m
2026-07-10 UAL82 EWR → DEL Jul 10, 02:24 UTCJul 10, 16:14 UTC13h 50m
2026-07-10 UAL82 - Jul 10, 02:25 UTCJul 10, 16:05 UTC13h 40m
2026-07-09 UAL713 SFO → EWR Jul 9, 18:55 UTCJul 9, 23:45 UTC4h 50m
2026-07-09 UAL61 - Jul 9, 01:05 UTCJul 9, 14:30 UTC13h 25m
2026-07-08 UAL60 SFO → MEL Jul 8, 07:10 UTCJul 8, 22:05 UTC14h 55m
2026-07-07 UAL1227 EWR → SFO Jul 7, 17:50 UTCJul 7, 23:00 UTC5h 10m
2026-07-07 UAL123 - Jul 7, 13:10 UTCJul 7, 14:45 UTC1h 35m
2026-07-07 UAL123 - Jul 7, 07:55 UTCJul 7, 13:05 UTC5h 10m
2026-07-06 UAL122 EWR → LHR Jul 6, 14:15 UTCJul 6, 20:20 UTC6h 5m
2026-07-05 UAL222D CPT → EWR Jul 5, 09:25 UTCJul 6, 00:20 UTC14h 55m
2026-07-04 UAL122D - Jul 4, 16:55 UTCJul 5, 06:25 UTC13h 30m
2026-07-03 UAL1855 LAX → EWR Jul 3, 23:20 UTCJul 4, 04:00 UTC4h 40m
2026-07-03 UAL3908 - Jul 3, 08:40 UTCJul 3, 21:10 UTC12h 30m
2026-07-02 UAL153 HKG → LAX Jul 2, 02:20 UTCJul 2, 02:25 UTC5m
2026-07-01 UAL152 LAX → HKG Jul 1, 13:00 UTCJul 1, 13:15 UTC15m
2026-07-01 UAL152 LAX → HKG Jul 1, 12:49 UTCJul 1, 15:01 UTC2h 12m

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 N29981 page for operator, model, and routing details .

Mode-S A31A73 frequently asked

What is Mode-S code A31A73?
A31A73 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N29981.
Where is Mode-S A31A73 registered?
Mode-S code A31A73 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 A31A73 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 20:10 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A31A73, octal 50615163, decimal 10,689,139.
What flights does A31A73 operate?
Mode-S A31A73 has broadcast 20 distinct callsigns, including UAL152, UAL153, UAL198, UAL842, UAL199.