Apparatus

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sensors Mode-S transponder

A81001

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N61882 · BOEING 737-900 · operated by UNITED AIRLINES INC

Hex
A81001
Octal
52010001
Decimal
11,014,145
Country
US
Tail
N61882
Type
B739
No current signal · last broadcast Jul 26, 22:15 UTC
Flights observed
417
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:15 UTC

Last known position

Most recent position reported by Mode-S A81001.

Country allocation

The ICAO 24-bit address A81001 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
UAL2736 - 5 2026-06-27
UAL758 - 4 2026-07-11
UAL659 United Airlines 4 2026-06-14
UAL2737 - 4 2026-06-27
UAL2624 United Airlines 4 2026-07-26
UAL2498 - 4 2026-07-17
UAL1916 - 4 2026-06-22
UAL1686 - 4 2026-07-13
UAL1576 - 4 2026-07-12
UAL1458 United Airlines 4 2026-05-02
UAL1168 United Airlines 4 2026-05-19
UAL733 United Airlines 3 2026-06-05
UAL559 United Airlines 3 2026-05-09
UAL444 United Airlines 3 2026-07-18
UAL382 - 3 2026-07-17
UAL279 - 3 2026-07-11
UAL2672 United Airlines 3 2026-06-13
UAL2646 United Airlines 3 2026-06-06
UAL2443 - 3 2026-07-14
UAL2370 United Airlines 3 2026-05-06

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1900 COS → DEN Jul 26, 21:15 UTCJul 26, 22:15 UTC1h 0m
2026-07-26 UAL2624 LGA → DEN Jul 26, 19:05 UTCJul 26, 19:10 UTC5m
2026-07-26 UAL2624 LGA → DEN Jul 26, 16:25 UTCJul 26, 19:10 UTC2h 45m
2026-07-26 UAL2624 LGA → DEN Jul 26, 16:29 UTCJul 26, 18:49 UTC2h 20m
2026-07-26 UAL1115 DEN → MCI Jul 26, 12:35 UTCJul 26, 15:05 UTC2h 30m
2026-07-26 UAL2767 MCO → ORD Jul 26, 01:55 UTCJul 26, 05:00 UTC3h 5m
2026-07-25 UAL1092 PHL → ORD Jul 25, 20:55 UTCJul 25, 23:55 UTC3h 0m
2026-07-25 UAL1308 EWR → ATL Jul 25, 17:15 UTCJul 25, 19:40 UTC2h 25m
2026-07-25 UAL1500 RDU → EWR Jul 25, 14:20 UTCJul 25, 15:55 UTC1h 35m
2026-07-25 UAL2324 GEG → SFO Jul 25, 00:20 UTCJul 25, 01:45 UTC1h 25m
2026-07-24 UAL1126 LAS → EWR Jul 24, 19:45 UTCJul 24, 22:55 UTC3h 10m
2026-07-23 UAL1997 AUA → EWR Jul 23, 00:05 UTCJul 23, 01:50 UTC1h 45m
2026-07-22 UAL1101 IAD → MCO Jul 22, 20:45 UTCJul 22, 22:40 UTC1h 55m
2026-07-22 UAL2054 MSY → IAH Jul 22, 17:10 UTCJul 22, 19:00 UTC1h 50m
2026-07-22 UAL1406 EWR → CHS Jul 22, 14:05 UTCJul 22, 16:05 UTC2h 0m
2026-07-21 UAL1279 EWR → SFO Jul 21, 12:45 UTCJul 21, 16:15 UTC3h 30m
2026-07-21 UAL1218 EWR → LAS Jul 21, 03:40 UTCJul 21, 05:45 UTC2h 5m
2026-07-21 UAL8197 SFO → SEA Jul 21, 00:35 UTCJul 21, 02:10 UTC1h 35m
2026-07-20 UAL1799 MIA → EWR Jul 20, 21:40 UTCJul 20, 22:45 UTC1h 5m
2026-07-20 UAL611J SFO → LAS Jul 20, 18:25 UTCJul 20, 19:40 UTC1h 15m
2026-07-20 UAL611J SFO → LAS Jul 20, 18:26 UTCJul 20, 19:40 UTC1h 14m
2026-07-20 UAL2322 IAH → CMH Jul 20, 15:00 UTCJul 20, 17:00 UTC2h 0m
2026-07-20 UAL2191 - Jul 20, 02:35 UTCJul 20, 04:50 UTC2h 15m
2026-07-19 UAL684 - Jul 19, 19:35 UTCJul 20, 00:15 UTC4h 40m
2026-07-19 UAL2081 LAX → IAD Jul 19, 13:30 UTCJul 19, 18:10 UTC4h 40m
2026-07-19 UAL1385 JAC → DEN Jul 19, 05:35 UTCJul 19, 10:10 UTC4h 35m
2026-07-18 UAL444 BNA → IAD Jul 18, 21:25 UTCJul 19, 02:05 UTC4h 40m
2026-07-18 UAL444 BNA → IAD Jul 18, 21:26 UTCJul 19, 02:07 UTC4h 41m
2026-07-18 UAL2177 - Jul 18, 18:55 UTCJul 18, 20:05 UTC1h 10m
2026-07-18 UAL2356 BUR → SFO Jul 18, 15:55 UTCJul 18, 17:00 UTC1h 5m
2026-07-18 UAL1995 SFO → LAS Jul 18, 03:25 UTCJul 18, 04:40 UTC1h 15m
2026-07-17 UAL382 - Jul 17, 22:10 UTCJul 18, 01:25 UTC3h 15m
2026-07-17 UAL382 - Jul 17, 21:50 UTCJul 17, 22:05 UTC15m
2026-07-17 UAL2498 - Jul 17, 16:15 UTCJul 17, 19:49 UTC3h 35m
2026-07-17 UAL2498 SFO → IAH Jul 17, 16:17 UTCJul 17, 19:48 UTC3h 31m
2026-07-17 UAL487 - Jul 17, 10:40 UTCJul 17, 14:04 UTC3h 25m
2026-07-17 UAL387 - Jul 17, 02:30 UTCJul 17, 05:20 UTC2h 50m
2026-07-16 UAL684 - Jul 16, 19:50 UTCJul 17, 00:30 UTC4h 40m
2026-07-16 UAL2081 - Jul 16, 13:10 UTCJul 16, 17:49 UTC4h 40m
2026-07-15 UAL2373 - Jul 15, 11:20 UTCJul 15, 14:50 UTC3h 30m
2026-07-15 UAL1672 LAS → ORD Jul 15, 02:30 UTCJul 15, 05:40 UTC3h 10m
2026-07-14 UAL1875 ORD → LAS Jul 14, 21:45 UTCJul 15, 00:40 UTC2h 54m
2026-07-14 UAL2443 - Jul 14, 18:40 UTCJul 14, 19:25 UTC45m
2026-07-14 UAL2389 - Jul 14, 15:40 UTCJul 14, 16:30 UTC50m
2026-07-14 UAL567 - Jul 14, 12:40 UTCJul 14, 13:40 UTC1h 0m
2026-07-14 UAL1131 ORD → MSP Jul 14, 02:55 UTCJul 14, 03:50 UTC55m
2026-07-14 UAL1131 ORD → MSP Jul 14, 03:01 UTCJul 14, 03:49 UTC48m
2026-07-13 UAL1686 PHX → ORD Jul 13, 21:55 UTCJul 14, 01:05 UTC3h 10m
2026-07-13 UAL370 EWR → PHX Jul 13, 15:30 UTCJul 13, 19:45 UTC4h 15m
2026-07-13 UAL2603 - Jul 13, 11:15 UTCJul 13, 13:45 UTC2h 30m

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 N61882 page for operator, model, and routing details .

Mode-S A81001 frequently asked

What is Mode-S code A81001?
A81001 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N61882.
Where is Mode-S A81001 registered?
Mode-S code A81001 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 A81001 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A81001, octal 52010001, decimal 11,014,145.
What flights does A81001 operate?
Mode-S A81001 has broadcast 20 distinct callsigns, including UAL2736, UAL758, UAL659, UAL2737, UAL2624.