Apparatus

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sensors Mode-S transponder

AB8553

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N841UA · AIRBUS A-319 · operated by UNITED AIRLINES INC

Hex
AB8553
Octal
52702523
Decimal
11,240,787
Country
US
Tail
N841UA
Type
A319
No current signal · last broadcast Jul 26, 22:45 UTC
Flights observed
546
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:45 UTC

Last known position

Most recent position reported by Mode-S AB8553.

Country allocation

The ICAO 24-bit address AB8553 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
UAL1639 - 10 2026-07-02
UAL412 - 9 2026-06-25
UAL2729 - 7 2026-07-12
UAL481 - 6 2026-07-11
UAL2690 - 6 2026-07-06
UAL2465 United Airlines 6 2026-04-15
UAL1499 United Airlines 6 2026-06-14
UAL657 United Airlines 5 2026-07-25
UAL2115 United Airlines 5 2026-07-20
UAL2097 - 5 2026-06-25
UAL1848 - 5 2026-06-14
UAL1229 United Airlines 5 2026-06-14
UAL786 - 4 2026-07-14
UAL373 United Airlines 4 2026-05-18
UAL365 - 4 2026-07-03
UAL2728 - 4 2026-07-12
UAL2272 United Airlines 4 2026-05-09
UAL2187 United Airlines 4 2026-07-20
UAL1986 United Airlines 4 2026-05-19
UAL1451 - 4 2026-07-10

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1991 EWR → SFO Jul 26, 21:25 UTCJul 26, 22:45 UTC1h 20m
2026-07-26 UAL1900 COS → DEN Jul 26, 14:55 UTCJul 26, 19:25 UTC4h 30m
2026-07-26 UAL1796 EWR → ORD Jul 26, 01:13 UTCJul 26, 06:11 UTC4h 58m
2026-07-26 UAL1796 EWR → ORD Jul 26, 01:00 UTCJul 26, 06:20 UTC5h 20m
2026-07-25 UAL2359 IAD → BDL Jul 25, 17:50 UTCJul 25, 22:20 UTC4h 30m
2026-07-25 UAL1613 EWR → FLL Jul 25, 10:49 UTCJul 25, 16:05 UTC5h 16m
2026-07-25 UAL1613 EWR → FLL Jul 25, 10:40 UTCJul 25, 16:10 UTC5h 30m
2026-07-25 UAL657 CHS → EWR Jul 25, 00:57 UTCJul 25, 02:51 UTC1h 54m
2026-07-25 UAL657 CHS → EWR Jul 25, 00:50 UTCJul 25, 02:55 UTC2h 5m
2026-07-24 UAL2470 DEN → MCI Jul 24, 21:55 UTCJul 24, 23:25 UTC1h 30m
2026-07-24 UAL1541 IAH → LGA Jul 24, 18:12 UTCJul 24, 19:45 UTC1h 33m
2026-07-24 UAL1541 IAH → LGA Jul 24, 18:05 UTCJul 24, 19:50 UTC1h 45m
2026-07-24 UAL456 EWR → SRQ Jul 24, 14:20 UTCJul 24, 16:10 UTC1h 50m
2026-07-24 UAL1268 LGA → IAH Jul 24, 01:10 UTCJul 24, 03:25 UTC2h 15m
2026-07-24 UAL1268 LGA → IAH Jul 24, 01:01 UTCJul 24, 03:28 UTC2h 27m
2026-07-23 UAL1608 MSN → DEN Jul 23, 19:20 UTCJul 23, 21:15 UTC1h 55m
2026-07-23 UAL1637 MSP → EWR Jul 23, 15:30 UTCJul 23, 17:30 UTC2h 0m
2026-07-23 UAL2183 EWR → MSP Jul 23, 11:35 UTCJul 23, 14:10 UTC2h 35m
2026-07-23 UAL657 CHS → EWR Jul 23, 02:50 UTCJul 23, 04:40 UTC1h 50m
2026-07-23 UAL2470 DEN → MCI Jul 23, 00:00 UTCJul 23, 01:30 UTC1h 30m
2026-07-22 UAL352 IAD → BOS Jul 22, 21:00 UTCJul 22, 21:45 UTC45m
2026-07-22 UAL1772 EWR → MYR Jul 22, 18:15 UTCJul 22, 18:45 UTC30m
2026-07-22 UAL1521 IAD → MSY Jul 22, 14:20 UTCJul 22, 16:00 UTC1h 40m
2026-07-21 UAL549 BOS → ORD Jul 21, 23:50 UTCJul 22, 01:05 UTC1h 15m
2026-07-21 UAL2027 GTF → DEN Jul 21, 20:54 UTCJul 21, 22:11 UTC1h 17m
2026-07-21 UAL2128 SLC → SFO Jul 21, 17:55 UTCJul 21, 18:55 UTC1h 0m
2026-07-21 UAL1045 SLG → DEN Jul 21, 14:05 UTCJul 21, 15:40 UTC1h 35m
2026-07-21 UAL1045 XNA → DEN Jul 21, 14:07 UTCJul 21, 15:30 UTC1h 23m
2026-07-21 UAL1351 DEN → XNA Jul 21, 00:35 UTCJul 21, 01:55 UTC1h 20m
2026-07-20 UAL2187 SBA → SFO Jul 20, 20:20 UTCJul 20, 22:15 UTC1h 55m
2026-07-20 UAL2115 MIA → EWR Jul 20, 18:05 UTCJul 20, 18:55 UTC50m
2026-07-20 UAL2317 EWR → AUS Jul 20, 16:10 UTCJul 20, 17:00 UTC50m
2026-07-20 UAL1757 PIT → DEN Jul 20, 07:55 UTCJul 20, 08:25 UTC30m
2026-07-20 UAL1429 IAH → EWR Jul 20, 03:35 UTCJul 20, 06:40 UTC3h 5m
2026-07-19 UAL2057 - Jul 19, 22:00 UTCJul 20, 00:05 UTC2h 5m
2026-07-19 UAL688 - Jul 19, 18:00 UTCJul 19, 20:05 UTC2h 5m
2026-07-19 UAL2266 - Jul 19, 13:10 UTCJul 19, 14:45 UTC1h 35m
2026-07-18 UAL750 - Jul 18, 20:10 UTCJul 18, 23:45 UTC3h 35m
2026-07-18 UAL537T - Jul 18, 14:55 UTCJul 18, 18:30 UTC3h 35m
2026-07-18 UAL1085 - Jul 18, 11:05 UTCJul 18, 12:50 UTC1h 45m
2026-07-17 UAL1028 IAH → MEX Jul 17, 21:44 UTCJul 17, 23:30 UTC1h 45m
2026-07-17 UAL1072 - Jul 17, 15:05 UTCJul 17, 19:35 UTC4h 30m
2026-07-17 UAL1982 - Jul 17, 11:35 UTCJul 17, 13:25 UTC1h 50m
2026-07-17 UAL1982 DSM → IAH Jul 17, 11:40 UTCJul 17, 13:31 UTC1h 51m
2026-07-17 UAL1780 - Jul 17, 01:29 UTCJul 17, 03:14 UTC1h 45m
2026-07-16 UAL1420 - Jul 16, 21:45 UTCJul 16, 23:55 UTC2h 10m
2026-07-16 UAL587 ORD → IND Jul 16, 20:00 UTCJul 16, 20:35 UTC35m
2026-07-16 UAL600 CBF → ORD Jul 16, 16:30 UTCJul 16, 17:45 UTC1h 15m
2026-07-16 UAL1778 - Jul 16, 14:00 UTCJul 16, 15:05 UTC1h 5m
2026-07-16 UAL2849 - Jul 16, 10:29 UTCJul 16, 12:14 UTC1h 45m

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 N841UA page for operator, model, and routing details .

Mode-S AB8553 frequently asked

What is Mode-S code AB8553?
AB8553 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N841UA.
Where is Mode-S AB8553 registered?
Mode-S code AB8553 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 AB8553 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:45 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AB8553, octal 52702523, decimal 11,240,787.
What flights does AB8553 operate?
Mode-S AB8553 has broadcast 20 distinct callsigns, including UAL1639, UAL412, UAL2729, UAL481, UAL2690.