Apparatus

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sensors Mode-S transponder

ABACD2

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N851UA · AIRBUS A-319 · operated by UNITED AIRLINES INC

Hex
ABACD2
Octal
52726322
Decimal
11,250,898
Country
US
Tail
N851UA
Type
A319
No current signal · last broadcast Jul 22, 02:15 UTC
Flights observed
429
Distinct callsigns
20
Country
US
Last broadcast
Jul 22, 02:15 UTC

Last known position

Most recent position reported by Mode-S ABACD2.

Country allocation

The ICAO 24-bit address ABACD2 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
UAL2347 United Airlines 6 2026-06-10
UAL591 United Airlines 5 2026-06-10
UAL2343 United Airlines 5 2026-07-19
UAL1439 - 5 2026-07-09
UAL1307 - 5 2026-06-18
UAL1067 United Airlines 5 2026-07-19
UAL745 - 4 2026-07-14
UAL676 United Airlines 4 2026-06-11
UAL657 - 4 2026-07-03
UAL2470 - 4 2026-07-02
UAL2198 - 4 2026-06-30
UAL2172 - 4 2026-06-25
UAL1991 - 4 2026-06-19
UAL1760 United Airlines 4 2026-06-11
UAL1365 - 4 2026-06-18
UAL1297 United Airlines 4 2026-05-17
UAL1060 - 4 2026-07-01
UAL8194 - 3 2026-04-13
UAL652 - 3 2026-07-02
UAL555 - 3 2026-06-19

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-21 UAL1863 PUJ → ORD Jul 21, 21:40 UTCJul 22, 02:10 UTC4h 30m
2026-07-21 UAL1642 SFO → DTW Jul 21, 16:00 UTCJul 21, 20:00 UTC4h 0m
2026-07-21 UAL1429 IAH → EWR Jul 21, 03:20 UTCJul 21, 06:20 UTC3h 0m
2026-07-21 UAL1429 IAH → EWR Jul 21, 03:00 UTCJul 21, 06:16 UTC3h 16m
2026-07-20 UAL2057 - Jul 20, 21:40 UTCJul 20, 23:50 UTC2h 10m
2026-07-20 UAL688 IAD → BOS Jul 20, 17:55 UTCJul 20, 19:55 UTC2h 0m
2026-07-20 UAL1484 LAX → SFO Jul 20, 14:05 UTCJul 20, 15:00 UTC55m
2026-07-20 UAL1148 DEN → BOS Jul 20, 07:00 UTCJul 20, 10:35 UTC3h 35m
2026-07-20 UAL1828 ORD → SAT Jul 20, 01:10 UTCJul 20, 04:55 UTC3h 45m
2026-07-19 UAL1067 IAH → BOS Jul 19, 21:55 UTCJul 19, 23:35 UTC1h 40m
2026-07-19 UAL2343 RSW → DEN Jul 19, 19:15 UTCJul 19, 20:30 UTC1h 15m
2026-07-19 UAL2343 RSW → DEN Jul 19, 19:24 UTCJul 19, 20:35 UTC1h 11m
2026-07-19 UAL2451 - Jul 19, 13:45 UTCJul 19, 17:25 UTC3h 40m
2026-07-19 UAL481 ORD → SJC Jul 19, 04:05 UTCJul 19, 07:55 UTC3h 50m
2026-07-19 UAL1067 IAH → BOS Jul 19, 01:10 UTCJul 19, 02:50 UTC1h 40m
2026-07-18 UAL2343 RSW → DEN Jul 18, 19:50 UTCJul 18, 21:10 UTC1h 20m
2026-07-18 UAL2451 SJC → ORD Jul 18, 13:50 UTCJul 18, 17:40 UTC3h 50m
2026-07-18 UAL481 - Jul 18, 04:35 UTCJul 18, 08:10 UTC3h 35m
2026-07-18 UAL1067 IAH → BOS Jul 18, 00:29 UTCJul 18, 02:19 UTC1h 50m
2026-07-17 UAL2343 RSW → DEN Jul 17, 20:04 UTCJul 17, 21:20 UTC1h 15m
2026-07-17 UAL2451 SJC → ORD Jul 17, 13:45 UTCJul 17, 17:55 UTC4h 10m
2026-07-17 UAL481 - Jul 17, 02:25 UTCJul 17, 06:10 UTC3h 45m
2026-07-16 UAL1067 IAH → BOS Jul 16, 22:19 UTCJul 17, 00:10 UTC1h 50m
2026-07-16 UAL1067 IAH → BOS Jul 16, 22:00 UTCJul 16, 23:44 UTC1h 44m
2026-07-16 UAL2343 RSW → DEN Jul 16, 19:30 UTCJul 16, 20:45 UTC1h 15m
2026-07-16 UAL1410 - Jul 16, 17:00 UTCJul 16, 17:49 UTC50m
2026-07-16 UAL1410 DSM → ORD Jul 16, 16:49 UTCJul 16, 17:46 UTC57m
2026-07-16 UAL1803 - Jul 16, 13:54 UTCJul 16, 14:40 UTC45m
2026-07-15 UAL2148 - Jul 15, 22:55 UTCJul 16, 00:25 UTC1h 30m
2026-07-15 UAL1314 ORD → DCA Jul 15, 20:05 UTCJul 15, 21:25 UTC1h 20m
2026-07-15 UAL1314 ORD → DCA Jul 15, 19:33 UTCJul 15, 21:23 UTC1h 50m
2026-07-15 UAL1660 - Jul 15, 15:50 UTCJul 15, 16:20 UTC30m
2026-07-15 UAL2093 - Jul 15, 14:10 UTCJul 15, 14:35 UTC25m
2026-07-15 UAL1517 DFW → ORD Jul 15, 01:35 UTCJul 15, 03:25 UTC1h 50m
2026-07-14 UAL793 ORD → DFW Jul 14, 22:40 UTCJul 15, 00:25 UTC1h 44m
2026-07-14 UAL745 - Jul 14, 20:35 UTCJul 14, 20:45 UTC10m
2026-07-14 UAL745 ATL → ORD Jul 14, 19:15 UTCJul 14, 20:45 UTC1h 30m
2026-07-14 UAL745 ATL → ORD Jul 14, 19:12 UTCJul 14, 20:20 UTC1h 8m
2026-07-14 UAL530 - Jul 14, 16:25 UTCJul 14, 17:50 UTC1h 25m
2026-07-14 UAL2137 - Jul 14, 14:45 UTCJul 14, 15:10 UTC25m
2026-07-14 UAL1178 - Jul 14, 01:05 UTCJul 14, 01:35 UTC30m
2026-07-13 UAL2729 MTY → ORD Jul 13, 18:50 UTCJul 13, 21:50 UTC3h 0m
2026-07-13 UAL2729 MTY → ORD Jul 13, 18:54 UTCJul 13, 21:31 UTC2h 37m
2026-07-13 UAL2728 ORD → MTY Jul 13, 14:40 UTCJul 13, 17:30 UTC2h 50m
2026-07-13 UAL1148 SMF → ORD Jul 13, 06:50 UTCJul 13, 10:30 UTC3h 40m
2026-07-13 UAL1828 ORD → SMF Jul 13, 01:30 UTCJul 13, 05:10 UTC3h 40m
2026-07-12 UAL658 MSP → ORD Jul 12, 22:25 UTCJul 12, 23:20 UTC55m
2026-07-12 UAL2298 - Jul 12, 20:15 UTCJul 12, 21:10 UTC55m
2026-07-12 UAL511 DCA → ORD Jul 12, 17:20 UTCJul 12, 19:01 UTC1h 40m
2026-07-12 UAL2218 ORD → DCA Jul 12, 14:30 UTCJul 12, 15:55 UTC1h 25m

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 N851UA page for operator, model, and routing details .

Mode-S ABACD2 frequently asked

What is Mode-S code ABACD2?
ABACD2 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N851UA.
Where is Mode-S ABACD2 registered?
Mode-S code ABACD2 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 ABACD2 broadcasting right now?
No active broadcast right now. Last signal was Jul 22, 02:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex ABACD2, octal 52726322, decimal 11,250,898.
What flights does ABACD2 operate?
Mode-S ABACD2 has broadcast 20 distinct callsigns, including UAL2347, UAL591, UAL2343, UAL1439, UAL1307.