Apparatus

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sensors Mode-S transponder

A254FF

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N24988 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC

Hex
A254FF
Octal
50452377
Decimal
10,638,591
Country
US
Tail
N24988
Type
B789
No current signal · last broadcast Jul 26, 18:25 UTC
Flights observed
198
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 18:25 UTC

Last known position

Most recent position reported by Mode-S A254FF.

Country allocation

The ICAO 24-bit address A254FF 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
UAL863 - 10 2026-07-10
UAL892 United Airlines 9 2026-07-26
UAL187 - 9 2026-06-26
UAL1011 United Airlines 9 2026-05-31
UAL893 United Airlines 8 2026-07-25
UAL2023 United Airlines 8 2026-06-01
UAL870 United Airlines 6 2026-07-18
UAL806 United Airlines 6 2026-07-21
UAL805 - 6 2026-07-20
UAL60 United Airlines 6 2026-07-24
UAL188 United Airlines 6 2026-06-26
UAL1849 United Airlines 6 2026-06-29
UAL1757 - 6 2026-06-29
UAL61 United Airlines 5 2026-07-25
UAL199 - 5 2026-07-16
UAL198 - 5 2026-07-15
UAL83 United Airlines 4 2026-07-06
UAL1593 United Airlines 4 2026-06-12
UAL123 - 4 2026-07-08
UAL839 - 3 2026-07-17

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL892 ICN → SFO Jul 26, 08:05 UTCJul 26, 09:55 UTC1h 50m
2026-07-26 UAL892 ICN → SFO Jul 26, 08:16 UTCJul 26, 18:13 UTC9h 57m
2026-07-25 UAL893 SFO → ICN Jul 25, 18:35 UTCJul 26, 05:55 UTC11h 20m
2026-07-25 UAL61 BRU → IAH Jul 25, 01:30 UTCJul 25, 15:05 UTC13h 35m
2026-07-24 UAL60 SFO → MEL Jul 24, 07:20 UTCJul 24, 22:30 UTC15h 10m
2026-07-23 UAL969 AMS → SFO Jul 23, 13:10 UTCJul 23, 23:40 UTC10h 30m
2026-07-22 UAL968 SFO → AMS Jul 22, 23:00 UTCJul 23, 08:25 UTC9h 25m
2026-07-22 UAL892 ICN → SFO Jul 22, 17:50 UTCJul 22, 18:50 UTC1h 0m
2026-07-22 UAL892 ICN → SFO Jul 22, 08:16 UTCJul 22, 18:47 UTC10h 31m
2026-07-21 UAL893 SFO → ICN Jul 21, 18:25 UTCJul 22, 05:25 UTC11h 0m
2026-07-21 UAL806 ICN → SFO Jul 21, 02:50 UTCJul 21, 13:45 UTC10h 55m
2026-07-20 UAL805 SFO → ICN Jul 20, 08:00 UTCJul 20, 19:15 UTC11h 15m
2026-07-19 UAL28 SIN → SFO Jul 19, 15:45 UTCJul 20, 04:40 UTC12h 55m
2026-07-19 UAL28 SIN → SFO Jul 19, 13:06 UTCJul 20, 04:50 UTC15h 44m
2026-07-18 UAL29 - Jul 18, 19:15 UTCJul 19, 09:10 UTC13h 55m
2026-07-18 UAL870 SYD → SFO Jul 18, 13:50 UTCJul 18, 13:55 UTC5m
2026-07-18 UAL870 SYD → SFO Jul 18, 00:45 UTCJul 18, 13:35 UTC12h 50m
2026-07-18 UAL870 SYD → SFO Jul 18, 00:35 UTCJul 18, 01:15 UTC40m
2026-07-17 UAL839 - Jul 17, 21:34 UTCJul 17, 21:39 UTC5m
2026-07-17 UAL839 - Jul 17, 07:14 UTCJul 17, 07:50 UTC35m
2026-07-17 UAL839 LAX → SYD Jul 17, 06:24 UTCJul 17, 21:15 UTC14h 51m
2026-07-16 UAL199 PVG → LAX Jul 16, 12:31 UTCJul 16, 23:54 UTC11h 23m
2026-07-16 UAL199 - Jul 16, 06:15 UTCJul 17, 00:04 UTC17h 50m
2026-07-15 UAL198 - Jul 15, 20:35 UTCJul 16, 14:55 UTC18h 20m
2026-07-15 UAL33 - Jul 15, 08:05 UTCJul 15, 17:35 UTC9h 30m
2026-07-15 UAL33 NRT → LAX Jul 15, 08:05 UTCJul 15, 17:26 UTC9h 21m
2026-07-14 UAL7 - Jul 14, 16:15 UTCJul 15, 04:50 UTC12h 34m
2026-07-14 UAL63 - Jul 14, 01:05 UTCJul 14, 10:45 UTC9h 40m
2026-07-13 UAL62 - Jul 13, 00:01 UTCJul 13, 09:30 UTC9h 30m
2026-07-12 UAL6 - Jul 12, 09:05 UTCJul 12, 09:35 UTC30m
2026-07-12 UAL6 NRT → IAH Jul 12, 09:01 UTCJul 12, 20:15 UTC11h 14m
2026-07-11 UAL143 DEN → NRT Jul 11, 19:40 UTCJul 12, 06:45 UTC11h 5m
2026-07-11 UAL3938 - Jul 11, 16:10 UTCJul 11, 18:05 UTC1h 55m
2026-07-11 UAL3938 LAX → DEN Jul 11, 15:59 UTCJul 11, 18:04 UTC2h 5m
2026-07-10 UAL842 SYD → LAX Jul 10, 23:50 UTCJul 11, 13:05 UTC13h 15m
2026-07-10 UAL863 SFO → SYD Jul 10, 06:45 UTCJul 10, 20:48 UTC14h 3m
2026-07-10 UAL863 - Jul 10, 06:45 UTCJul 10, 19:45 UTC13h 0m
2026-07-08 UAL1227 EWR → SFO Jul 8, 17:55 UTCJul 8, 23:05 UTC5h 10m
2026-07-08 UAL123 LHR → EWR Jul 8, 06:55 UTCJul 8, 13:55 UTC7h 0m
2026-07-08 UAL123 LHR → EWR Jul 8, 07:02 UTCJul 8, 13:57 UTC6h 55m
2026-07-07 UAL122 EWR → LHR Jul 7, 14:10 UTCJul 7, 20:30 UTC6h 20m
2026-07-06 UAL83 DEL → EWR Jul 6, 18:40 UTCJul 7, 05:45 UTC11h 5m
2026-07-06 UAL83 DEL → EWR Jul 6, 18:32 UTCJul 7, 10:24 UTC15h 52m
2026-07-06 UAL83 DEL → EWR Jul 6, 18:32 UTCJul 7, 10:19 UTC15h 47m
2026-07-06 UAL82 EWR → DEL Jul 6, 02:07 UTCJul 6, 16:28 UTC14h 21m
2026-07-06 UAL82 - Jul 6, 02:50 UTCJul 6, 16:15 UTC13h 25m
2026-07-04 UAL83 DEL → EWR Jul 4, 18:45 UTCJul 5, 10:35 UTC15h 50m
2026-07-04 UAL82 - Jul 4, 02:55 UTCJul 4, 16:10 UTC13h 15m
2026-07-03 UAL1173 SJU → EWR Jul 3, 20:00 UTCJul 3, 21:10 UTC1h 10m
2026-07-03 UAL1173 SJU → EWR Jul 3, 17:35 UTCJul 3, 17:50 UTC15m

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 N24988 page for operator, model, and routing details .

Mode-S A254FF frequently asked

What is Mode-S code A254FF?
A254FF is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N24988.
Where is Mode-S A254FF registered?
Mode-S code A254FF 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 A254FF broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 18:25 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A254FF, octal 50452377, decimal 10,638,591.
What flights does A254FF operate?
Mode-S A254FF has broadcast 20 distinct callsigns, including UAL863, UAL892, UAL187, UAL1011, UAL893.