Apparatus

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sensors Mode-S transponder

A55B3C

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N444UA · AIRBUS A-320 · operated by UNITED AIRLINES INC

Hex
A55B3C
Octal
51255474
Decimal
10,836,796
Country
US
Tail
N444UA
Type
A320
No current signal · last broadcast Jul 26, 22:25 UTC
Flights observed
314
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:25 UTC

Last known position

Most recent position reported by Mode-S A55B3C.

Country allocation

The ICAO 24-bit address A55B3C 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
UAL790 - 6 2026-07-19
UAL671 - 6 2026-07-16
UAL2866 United Airlines 5 2026-07-21
UAL576 - 4 2026-06-14
UAL365 - 4 2026-06-28
UAL357 - 4 2026-07-11
UAL2850 United Airlines 4 2026-07-21
UAL2447 - 4 2026-06-30
UAL2157 United Airlines 4 2026-07-25
UAL1613 United Airlines 4 2026-07-21
UAL1107 United Airlines 4 2026-06-28
UAL1088 United Airlines 4 2026-07-23
UAL822 - 3 2026-06-20
UAL412 - 3 2026-07-06
UAL292 - 3 2026-07-10
UAL2426 - 3 2026-06-13
UAL2340 United Airlines 3 2026-07-21
UAL2196 United Airlines 3 2026-07-24
UAL2192 United Airlines 3 2026-07-20
UAL215 United Airlines 3 2026-06-10

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1934 LAS → DEN Jul 26, 19:55 UTCJul 26, 22:25 UTC2h 30m
2026-07-26 UAL1366 IAD → DEN Jul 26, 16:15 UTCJul 26, 17:45 UTC1h 30m
2026-07-26 UAL2174 IAD → BDL Jul 26, 12:55 UTCJul 26, 14:30 UTC1h 35m
2026-07-25 UAL579 SJD → IAH Jul 25, 17:10 UTCJul 25, 23:15 UTC6h 5m
2026-07-25 UAL2366 SFO → LAS Jul 25, 13:05 UTCJul 25, 15:35 UTC2h 30m
2026-07-25 UAL2157 SEA → SFO Jul 25, 02:10 UTCJul 25, 04:55 UTC2h 45m
2026-07-25 UAL2157 SEA → SFO Jul 25, 02:15 UTCJul 25, 04:51 UTC2h 36m
2026-07-24 UAL1166 SAN → EWR Jul 24, 21:06 UTCJul 24, 23:05 UTC1h 59m
2026-07-24 UAL1166 SAN → EWR Jul 24, 17:35 UTCJul 24, 23:10 UTC5h 35m
2026-07-24 UAL2196 AUS → IAH Jul 24, 14:50 UTCJul 24, 15:35 UTC45m
2026-07-24 UAL2016 BDL → ORD Jul 24, 13:00 UTCJul 24, 13:30 UTC30m
2026-07-24 UAL1966 MSY → EWR Jul 24, 10:40 UTCJul 24, 11:20 UTC40m
2026-07-24 UAL8174 YVR → SFO Jul 24, 01:05 UTCJul 24, 01:35 UTC30m
2026-07-23 UAL1838 MEX → IAH Jul 23, 20:35 UTCJul 23, 22:20 UTC1h 45m
2026-07-23 UAL1088 IAH → MEX Jul 23, 17:05 UTCJul 23, 19:00 UTC1h 55m
2026-07-23 UAL1088 IAH → MEX Jul 23, 17:09 UTCJul 23, 18:58 UTC1h 49m
2026-07-23 UAL2662 DEN → PDX Jul 23, 13:15 UTCJul 23, 15:05 UTC1h 50m
2026-07-23 UAL8136 FLL → EWR Jul 23, 01:15 UTCJul 23, 02:25 UTC1h 10m
2026-07-22 UAL1790 EWR → MYR Jul 22, 20:50 UTCJul 22, 23:35 UTC2h 45m
2026-07-22 UAL1790 EWR → MYR Jul 22, 20:46 UTCJul 22, 23:26 UTC2h 40m
2026-07-22 UAL8170 SBP → LAX Jul 22, 18:40 UTCJul 22, 19:20 UTC40m
2026-07-22 UAL2177 PDX → ORD Jul 22, 11:10 UTCJul 22, 15:40 UTC4h 30m
2026-07-21 UAL2836 SFO → PIT Jul 21, 15:50 UTCJul 21, 20:25 UTC4h 35m
2026-07-21 UAL2340 ORD → MCO Jul 21, 13:50 UTCJul 21, 14:30 UTC40m
2026-07-21 UAL2866 LAX → CLE Jul 21, 05:15 UTCJul 21, 06:00 UTC45m
2026-07-21 UAL2850 JAX → ORD Jul 21, 02:55 UTCJul 21, 04:00 UTC1h 5m
2026-07-21 UAL2850 JAX → ORD Jul 21, 02:57 UTCJul 21, 03:52 UTC55m
2026-07-21 UAL1613 EWR → FLL Jul 21, 01:00 UTCJul 21, 01:35 UTC35m
2026-07-20 UAL737 - Jul 20, 21:35 UTCJul 20, 23:30 UTC1h 55m
2026-07-20 UAL2192 PHL → ORD Jul 20, 18:40 UTCJul 20, 20:05 UTC1h 25m
2026-07-20 UAL1578 SEA → SFO Jul 20, 15:40 UTCJul 20, 17:30 UTC1h 50m
2026-07-20 UAL1577 RNO → SFO Jul 20, 02:35 UTCJul 20, 04:05 UTC1h 30m
2026-07-19 UAL442 DEN → LGA Jul 19, 21:05 UTCJul 20, 00:20 UTC3h 15m
2026-07-19 UAL1326 SFO → BNA Jul 19, 16:25 UTCJul 19, 19:35 UTC3h 10m
2026-07-19 UAL790 DFW → SFO Jul 19, 11:15 UTCJul 19, 14:20 UTC3h 5m
2026-07-19 UAL1673 - Jul 19, 04:40 UTCJul 19, 06:35 UTC1h 55m
2026-07-19 UAL1564 DFW → ORD Jul 19, 01:05 UTCJul 19, 03:05 UTC2h 0m
2026-07-18 UAL1062 DEN → SFO Jul 18, 17:10 UTCJul 18, 20:20 UTC3h 10m
2026-07-18 UAL2340 ORD → MCO Jul 18, 14:15 UTCJul 18, 14:55 UTC40m
2026-07-18 UAL2866 LAX → CLE Jul 18, 05:45 UTCJul 18, 06:30 UTC45m
2026-07-18 UAL2850 JAX → ORD Jul 18, 03:30 UTCJul 18, 04:30 UTC1h 0m
2026-07-18 UAL1613 EWR → FLL Jul 18, 01:20 UTCJul 18, 01:50 UTC30m
2026-07-17 UAL454 DFW → SFO Jul 17, 20:44 UTCJul 18, 00:00 UTC3h 15m
2026-07-17 UAL454 DFW → SFO Jul 17, 20:38 UTCJul 17, 23:55 UTC3h 17m
2026-07-17 UAL1062 DEN → SFO Jul 17, 16:00 UTCJul 17, 19:05 UTC3h 5m
2026-07-17 UAL335 EUG → SFO Jul 17, 13:10 UTCJul 17, 14:35 UTC1h 25m
2026-07-17 UAL1508 - Jul 17, 04:54 UTCJul 17, 06:00 UTC1h 5m
2026-07-17 UAL1508 BUR → SFO Jul 17, 02:45 UTCJul 17, 03:39 UTC55m
2026-07-16 UAL2764 HAF → BUR Jul 16, 23:49 UTCJul 17, 00:40 UTC50m
2026-07-16 UAL2305 SBA → SFO Jul 16, 22:00 UTCJul 16, 22:45 UTC45m

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 N444UA page for operator, model, and routing details .

Mode-S A55B3C frequently asked

What is Mode-S code A55B3C?
A55B3C is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N444UA.
Where is Mode-S A55B3C registered?
Mode-S code A55B3C 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 A55B3C broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:25 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A55B3C, octal 51255474, decimal 10,836,796.
What flights does A55B3C operate?
Mode-S A55B3C has broadcast 20 distinct callsigns, including UAL790, UAL671, UAL2866, UAL576, UAL365.