Apparatus

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sensors Mode-S transponder

A254D8

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N24974 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC

Hex
A254D8
Octal
50452330
Decimal
10,638,552
Country
US
Tail
N24974
Type
B789
Broadcasting now · callsign UAL177 · 41,000 ft
Flights observed
195
Distinct callsigns
20
Country
US
Last broadcast
1h ago

Current position

A254D8 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A254D8 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
UAL820 United Airlines 16 2026-05-21
UAL821 United Airlines 15 2026-05-21
UAL26 - 9 2026-07-13
UAL152 United Airlines 9 2026-05-24
UAL772 United Airlines 8 2026-05-23
UAL27 - 8 2026-07-12
UAL771 United Airlines 7 2026-05-22
UAL178 United Airlines 7 2026-07-07
UAL153 United Airlines 7 2026-05-25
UAL2 - 6 2026-06-16
UAL177 - 6 2026-07-14
UAL187 - 5 2026-06-19
UAL182 - 5 2026-07-11
UAL181 - 5 2026-07-12
UAL142 - 5 2026-07-10
UAL842 - 4 2026-06-21
UAL263 - 4 2026-06-30
UAL1227 - 4 2026-06-14
UAL1 - 4 2026-06-15
UAL893 United Airlines 3 2026-04-15

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 UAL177 - Jul 14, 00:20 UTCJul 14, 08:00 UTC7h 40m
2026-07-13 UAL26 - Jul 13, 11:05 UTCJul 13, 19:50 UTC8h 45m
2026-07-13 UAL26 LHR → DEN Jul 13, 10:50 UTCJul 13, 19:50 UTC9h 0m
2026-07-12 UAL27 DEN → LHR Jul 12, 23:50 UTCJul 13, 08:25 UTC8h 35m
2026-07-12 UAL181 FRA → DEN Jul 12, 09:45 UTCJul 12, 19:15 UTC9h 30m
2026-07-11 UAL182 DEN → FRA Jul 11, 22:15 UTCJul 12, 07:10 UTC8h 55m
2026-07-11 UAL181 - Jul 11, 09:35 UTCJul 11, 19:20 UTC9h 45m
2026-07-11 UAL181 FRA → DEN Jul 11, 09:41 UTCJul 11, 19:17 UTC9h 36m
2026-07-10 UAL182 - Jul 10, 22:10 UTCJul 11, 07:05 UTC8h 55m
2026-07-10 UAL142 - Jul 10, 08:35 UTCJul 10, 19:20 UTC10h 45m
2026-07-09 UAL143 DEN → NRT Jul 9, 18:04 UTCJul 10, 05:05 UTC11h 1m
2026-07-09 UAL143 - Jul 9, 17:55 UTCJul 10, 00:00 UTC6h 5m
2026-07-08 UAL761 - Jul 8, 14:40 UTCJul 9, 01:00 UTC10h 20m
2026-07-08 UAL760 - Jul 8, 03:00 UTCJul 8, 12:20 UTC9h 20m
2026-07-07 UAL178 KIX → GUM Jul 7, 23:25 UTCJul 8, 00:00 UTC35m
2026-07-07 UAL178 KIX → GUM Jul 7, 12:50 UTCJul 7, 15:25 UTC2h 35m
2026-07-07 UAL178 KIX → GUM Jul 7, 12:47 UTCJul 7, 23:10 UTC10h 23m
2026-07-07 UAL177 DEN → FCO Jul 7, 00:08 UTCJul 7, 10:37 UTC10h 29m
2026-07-07 UAL177 DEN → FCO Jul 7, 00:40 UTCJul 7, 10:40 UTC10h 0m
2026-07-06 UAL26 - Jul 6, 10:50 UTCJul 6, 20:00 UTC9h 10m
2026-07-06 UAL27 DEN → LHR Jul 6, 00:00 UTCJul 6, 08:25 UTC8h 25m
2026-07-05 UAL26 - Jul 5, 10:50 UTCJul 5, 19:50 UTC9h 0m
2026-07-04 UAL27 DEN → LHR Jul 4, 23:58 UTCJul 5, 08:17 UTC8h 19m
2026-07-04 UAL27 - Jul 4, 23:50 UTCJul 5, 01:40 UTC1h 50m
2026-07-04 UAL181 - Jul 4, 10:05 UTCJul 4, 19:45 UTC9h 40m
2026-07-03 UAL182 DEN → FRA Jul 3, 22:10 UTCJul 4, 06:40 UTC8h 30m
2026-07-03 UAL142 NRT → DEN Jul 3, 07:45 UTCJul 3, 18:05 UTC10h 20m
2026-07-02 UAL143 DEN → NRT Jul 2, 17:55 UTCJul 3, 05:00 UTC11h 5m
2026-07-01 UAL761 MUC → DEN Jul 1, 14:50 UTCJul 2, 00:50 UTC10h 0m
2026-07-01 UAL760 - Jul 1, 02:45 UTCJul 1, 12:10 UTC9h 25m
2026-06-30 UAL263 - Jun 30, 14:30 UTCJul 1, 00:00 UTC9h 30m
2026-06-30 UAL263 LHR → DEN Jun 30, 14:14 UTCJun 30, 23:53 UTC9h 39m
2026-06-30 UAL262 DEN → LHR Jun 30, 02:55 UTCJun 30, 11:25 UTC8h 30m
2026-06-29 UAL178 KIX → GUM Jun 29, 12:45 UTCJun 29, 23:44 UTC11h 0m
2026-06-29 UAL177 DEN → FCO Jun 29, 00:20 UTCJun 29, 10:00 UTC9h 40m
2026-06-28 UAL26 - Jun 28, 11:29 UTCJun 28, 20:19 UTC8h 50m
2026-06-28 UAL27 - Jun 28, 00:39 UTCJun 28, 09:10 UTC8h 30m
2026-06-27 UAL27 DEN → LHR Jun 27, 23:58 UTCJun 28, 09:00 UTC9h 2m
2026-06-27 UAL181 FRA → DEN Jun 27, 10:14 UTCJun 27, 19:45 UTC9h 30m
2026-06-26 UAL182 DEN → FRA Jun 26, 22:18 UTCJun 27, 07:01 UTC8h 43m
2026-06-26 UAL182 DEN → FRA Jun 26, 22:14 UTCJun 27, 07:19 UTC9h 5m
2026-06-26 UAL142 NRT → DEN Jun 26, 08:15 UTCJun 26, 08:45 UTC30m
2026-06-26 UAL142 NRT → DEN Jun 26, 08:00 UTCJun 26, 18:39 UTC10h 39m
2026-06-25 UAL7 - Jun 25, 15:59 UTCJun 26, 04:55 UTC12h 55m
2026-06-25 UAL63 - Jun 25, 01:14 UTCJun 25, 10:45 UTC9h 30m
2026-06-24 UAL62 - Jun 24, 00:05 UTCJun 24, 09:19 UTC9h 15m
2026-06-23 UAL6 - Jun 23, 08:25 UTCJun 23, 19:34 UTC11h 10m
2026-06-23 UAL6 NRT → IAH Jun 23, 08:26 UTCJun 23, 19:26 UTC11h 0m
2026-06-22 UAL32 - Jun 22, 18:15 UTCJun 23, 04:50 UTC10h 35m
2026-06-21 UAL842 - Jun 21, 23:59 UTCJun 22, 13:10 UTC13h 10m

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 N24974 page for operator, model, and routing details .

Mode-S A254D8 frequently asked

What is Mode-S code A254D8?
A254D8 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N24974.
Where is Mode-S A254D8 registered?
Mode-S code A254D8 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 A254D8 broadcasting right now?
Yes. Mode-S A254D8 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A254D8, octal 50452330, decimal 10,638,552.
What flights does A254D8 operate?
Mode-S A254D8 has broadcast 20 distinct callsigns, including UAL820, UAL821, UAL26, UAL152, UAL772.