Apparatus

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sensors Mode-S transponder

AB4531

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N825UA · AIRBUS A-319 · operated by UNITED AIRLINES INC

Hex
AB4531
Octal
52642461
Decimal
11,224,369
Country
US
Tail
N825UA
Type
A319
No current signal · last broadcast 3h ago
Flights observed
318
Distinct callsigns
20
Country
US
Last broadcast
3h ago

Last known position

Most recent position reported by Mode-S AB4531.

Country allocation

The ICAO 24-bit address AB4531 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
UAL2718 - 10 2026-07-13
UAL1334 - 8 2026-07-13
UAL1090 United Airlines 6 2026-06-03
UAL737 - 5 2026-07-11
UAL2836 - 5 2026-07-13
UAL1846 - 5 2026-07-04
UAL538 - 4 2026-07-11
UAL436 - 4 2026-07-13
UAL283 - 4 2026-07-10
UAL1963 - 4 2026-07-04
UAL1642 - 4 2026-07-11
UAL1367 - 4 2026-07-10
UAL1235 - 4 2026-06-24
UAL773 - 3 2026-06-22
UAL616 - 3 2026-07-04
UAL568 - 3 2026-07-02
UAL544 United Airlines 3 2026-05-17
UAL2468 United Airlines 3 2026-06-26
UAL2260 United Airlines 3 2026-06-03
UAL2232 - 3 2026-06-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 UAL436 - Jul 13, 21:40 UTCJul 14, 02:10 UTC4h 30m
2026-07-13 UAL2836 - Jul 13, 15:45 UTCJul 13, 20:20 UTC4h 35m
2026-07-13 UAL2718 - Jul 13, 13:35 UTCJul 13, 14:10 UTC35m
2026-07-13 UAL1334 SFO → SBP Jul 13, 04:18 UTCJul 13, 04:53 UTC35m
2026-07-13 UAL1334 SFO → SBP Jul 13, 04:10 UTCJul 13, 04:55 UTC45m
2026-07-12 UAL436 - Jul 12, 22:10 UTCJul 13, 02:50 UTC4h 40m
2026-07-12 UAL2836 - Jul 12, 16:05 UTCJul 12, 20:25 UTC4h 20m
2026-07-12 UAL2718 - Jul 12, 14:20 UTCJul 12, 14:55 UTC35m
2026-07-12 UAL2718 SBP → SFO Jul 12, 13:42 UTCJul 12, 14:50 UTC1h 8m
2026-07-12 UAL1334 SFO → SBP Jul 12, 04:23 UTCJul 12, 05:10 UTC47m
2026-07-12 UAL1334 - Jul 12, 04:15 UTCJul 12, 04:55 UTC40m
2026-07-11 UAL1863 - Jul 11, 21:35 UTCJul 12, 01:55 UTC4h 20m
2026-07-11 UAL1642 - Jul 11, 15:50 UTCJul 11, 20:05 UTC4h 15m
2026-07-11 UAL538 ABQ → SFO Jul 11, 12:10 UTCJul 11, 14:10 UTC2h 0m
2026-07-11 UAL737 SFO → ABQ Jul 11, 02:00 UTCJul 11, 03:50 UTC1h 50m
2026-07-10 UAL1367 MSP → SFO Jul 10, 20:55 UTCJul 11, 00:25 UTC3h 30m
2026-07-10 UAL283 - Jul 10, 16:10 UTCJul 10, 19:20 UTC3h 10m
2026-07-10 UAL538 ABQ → SFO Jul 10, 12:15 UTCJul 10, 14:20 UTC2h 5m
2026-07-10 UAL737 - Jul 10, 02:00 UTCJul 10, 03:50 UTC1h 50m
2026-07-10 UAL737 SFO → ABQ Jul 10, 02:12 UTCJul 10, 03:44 UTC1h 32m
2026-07-09 UAL1367 MSP → SFO Jul 9, 20:35 UTCJul 10, 00:20 UTC3h 45m
2026-07-09 UAL283 OAK → MSP Jul 9, 16:10 UTCJul 9, 19:15 UTC3h 5m
2026-07-09 UAL2718 - Jul 9, 14:00 UTCJul 9, 14:35 UTC35m
2026-07-09 UAL1334 SFO → SBP Jul 9, 04:15 UTCJul 9, 05:00 UTC45m
2026-07-09 UAL1334 ORD → SFO Jul 9, 04:28 UTCJul 9, 04:56 UTC28m
2026-07-08 UAL436 - Jul 8, 21:35 UTCJul 9, 02:30 UTC4h 55m
2026-07-08 UAL2836 - Jul 8, 15:45 UTCJul 8, 20:05 UTC4h 20m
2026-07-08 UAL2718 - Jul 8, 13:50 UTCJul 8, 14:35 UTC45m
2026-07-08 UAL1334 SFO → SBP Jul 8, 04:15 UTCJul 8, 04:55 UTC40m
2026-07-07 UAL1863 - Jul 7, 22:00 UTCJul 8, 03:00 UTC5h 0m
2026-07-07 UAL1642 - Jul 7, 16:10 UTCJul 7, 20:10 UTC4h 0m
2026-07-07 UAL538 ABQ → SFO Jul 7, 12:15 UTCJul 7, 14:20 UTC2h 5m
2026-07-07 UAL737 - Jul 7, 02:10 UTCJul 7, 04:00 UTC1h 50m
2026-07-06 UAL1367 MSP → SFO Jul 6, 21:30 UTCJul 7, 01:00 UTC3h 30m
2026-07-06 UAL283 - Jul 6, 17:15 UTCJul 6, 20:20 UTC3h 5m
2026-07-06 UAL2718 - Jul 6, 14:25 UTCJul 6, 14:30 UTC5m
2026-07-06 UAL2718 - Jul 6, 13:40 UTCJul 6, 14:30 UTC50m
2026-07-06 UAL2718 SBP → SFO Jul 6, 13:42 UTCJul 6, 14:10 UTC28m
2026-07-06 UAL1334 - Jul 6, 07:00 UTCJul 6, 07:40 UTC40m
2026-07-06 UAL436 PIT → SFO Jul 6, 00:55 UTCJul 6, 05:45 UTC4h 50m
2026-07-05 UAL2836 - Jul 5, 15:50 UTCJul 5, 20:20 UTC4h 30m
2026-07-05 UAL2836 SFO → PIT Jul 5, 15:55 UTCJul 5, 20:18 UTC4h 23m
2026-07-05 UAL2718 PDX → SFO Jul 5, 13:45 UTCJul 5, 14:30 UTC45m
2026-07-05 UAL2718 PDX → SFO Jul 5, 13:42 UTCJul 5, 14:27 UTC45m
2026-07-04 UAL1846 DEN → SBP Jul 4, 17:55 UTCJul 4, 20:05 UTC2h 10m
2026-07-04 UAL1963 - Jul 4, 12:50 UTCJul 4, 15:55 UTC3h 5m
2026-07-04 UAL1963 CLT → DEN Jul 4, 12:57 UTCJul 4, 15:57 UTC3h 0m
2026-07-04 UAL616 - Jul 4, 00:05 UTCJul 4, 02:55 UTC2h 50m
2026-07-03 UAL2325 MSY → DEN Jul 3, 19:40 UTCJul 3, 22:00 UTC2h 20m
2026-07-03 UAL2273 DEN → MSY Jul 3, 16:36 UTCJul 3, 18:47 UTC2h 11m

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 N825UA page for operator, model, and routing details .

Mode-S AB4531 frequently asked

What is Mode-S code AB4531?
AB4531 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N825UA.
Where is Mode-S AB4531 registered?
Mode-S code AB4531 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 AB4531 broadcasting right now?
No active broadcast right now. Last signal was 3h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AB4531, octal 52642461, decimal 11,224,369.
What flights does AB4531 operate?
Mode-S AB4531 has broadcast 20 distinct callsigns, including UAL2718, UAL1334, UAL1090, UAL737, UAL2836.