Apparatus

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sensors Mode-S transponder

A21679

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N2333U · BOEING 777-300ER · operated by UNITED AIRLINES INC

Hex
A21679
Octal
50413171
Decimal
10,622,585
Country
US
Tail
N2333U
Type
B77W
No current signal · last broadcast Jul 26, 10:25 UTC
Flights observed
246
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 10:25 UTC

Last known position

Most recent position reported by Mode-S A21679.

Country allocation

The ICAO 24-bit address A21679 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
UAL1175 - 16 2026-06-25
UAL43 - 15 2026-07-06
UAL809 United Airlines 14 2026-07-19
UAL862 United Airlines 12 2026-07-25
UAL950 - 11 2026-06-28
UAL877 United Airlines 11 2026-07-24
UAL810 United Airlines 11 2026-07-20
UAL201 - 11 2026-06-26
UAL42 - 10 2026-07-06
UAL869 United Airlines 9 2026-07-22
UAL951 United Airlines 8 2026-06-29
UAL878 United Airlines 8 2026-07-23
UAL871 United Airlines 8 2026-07-25
UAL200 - 8 2026-06-27
UAL189 - 8 2026-07-16
UAL989 - 7 2026-06-29
UAL190 - 7 2026-07-17
UAL988 - 6 2026-06-28
UAL872 - 5 2026-06-13
UAL1411 United Airlines 5 2026-05-17

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-25 UAL871 SFO → TPE Jul 25, 22:30 UTCJul 26, 10:25 UTC11h 56m
2026-07-25 UAL862 HKG → SFO Jul 25, 06:15 UTCJul 25, 16:40 UTC10h 25m
2026-07-25 UAL862 HKG → SFO Jul 25, 04:00 UTCJul 25, 04:15 UTC15m
2026-07-24 UAL877 SFO → HKG Jul 24, 07:40 UTCJul 24, 20:45 UTC13h 5m
2026-07-23 UAL878 HKG → SFO Jul 23, 14:55 UTCJul 23, 16:05 UTC1h 10m
2026-07-23 UAL878 HKG → SFO Jul 23, 14:51 UTCJul 24, 03:12 UTC12h 21m
2026-07-22 UAL869 SFO → HKG Jul 22, 21:12 UTCJul 23, 10:14 UTC13h 2m
2026-07-22 UAL869 SFO → HKG Jul 22, 21:10 UTCJul 23, 10:10 UTC13h 0m
2026-07-22 UAL862 HKG → SFO Jul 22, 04:11 UTCJul 22, 17:00 UTC12h 49m
2026-07-22 UAL862 HKG → SFO Jul 22, 04:15 UTCJul 22, 17:05 UTC12h 50m
2026-07-21 UAL877 SFO → HKG Jul 21, 07:33 UTCJul 21, 20:35 UTC13h 2m
2026-07-21 UAL877 SFO → HKG Jul 21, 07:30 UTCJul 21, 20:35 UTC13h 5m
2026-07-20 UAL810 PHL → DEN Jul 20, 13:41 UTCJul 21, 02:23 UTC12h 42m
2026-07-20 UAL810 PHL → DEN Jul 20, 13:50 UTCJul 21, 02:25 UTC12h 35m
2026-07-19 UAL809 SEA → IAD Jul 19, 22:05 UTCJul 20, 10:55 UTC12h 50m
2026-07-19 UAL858 ICN → SFO Jul 19, 04:44 UTCJul 19, 15:23 UTC10h 39m
2026-07-19 UAL858 ICN → SFO Jul 19, 05:10 UTCJul 19, 15:30 UTC10h 20m
2026-07-18 UAL857 - Jul 18, 06:20 UTCJul 19, 06:15 UTC23h 55m
2026-07-17 UAL857 SFO → PVG Jul 17, 20:57 UTCJul 18, 08:29 UTC11h 32m
2026-07-17 UAL857 - Jul 17, 20:55 UTCJul 18, 06:15 UTC9h 21m
2026-07-17 UAL190 - Jul 17, 01:00 UTCJul 17, 13:29 UTC12h 30m
2026-07-16 UAL189 - Jul 16, 08:40 UTCJul 16, 21:25 UTC12h 45m
2026-07-16 UAL189 SFO → MNL Jul 16, 08:34 UTCJul 16, 21:22 UTC12h 48m
2026-07-15 UAL878 HKG → SFO Jul 15, 14:50 UTCJul 16, 03:30 UTC12h 40m
2026-07-15 UAL869 - Jul 15, 10:10 UTCJul 15, 10:25 UTC15m
2026-07-14 UAL869 - Jul 14, 21:00 UTCJul 15, 09:30 UTC12h 29m
2026-07-14 UAL862 - Jul 14, 04:05 UTCJul 14, 16:45 UTC12h 40m
2026-07-13 UAL877 SFO → HKG Jul 13, 07:28 UTCJul 13, 20:48 UTC13h 20m
2026-07-13 UAL877 - Jul 13, 07:50 UTCJul 13, 18:15 UTC10h 25m
2026-07-12 UAL810 - Jul 12, 13:50 UTCJul 13, 02:25 UTC12h 35m
2026-07-11 UAL809 SFO → MNL Jul 11, 21:43 UTCJul 12, 10:43 UTC13h 0m
2026-07-11 UAL809 - Jul 11, 21:35 UTCJul 12, 10:15 UTC12h 40m
2026-07-11 UAL1960 EWR → SFO Jul 11, 11:20 UTCJul 11, 16:35 UTC5h 15m
2026-07-10 UAL78 - Jul 10, 08:50 UTCJul 10, 20:55 UTC12h 5m
2026-07-09 UAL79 EWR → NRT Jul 9, 16:02 UTCJul 10, 04:42 UTC12h 40m
2026-07-09 UAL79 EWR → NRT Jul 9, 16:00 UTCJul 10, 04:45 UTC12h 45m
2026-07-09 UAL2416 SFO → EWR Jul 9, 07:51 UTCJul 9, 12:40 UTC4h 49m
2026-07-09 UAL2416 SFO → EWR Jul 9, 07:50 UTCJul 9, 12:45 UTC4h 55m
2026-07-08 UAL810 - Jul 8, 13:50 UTCJul 9, 02:05 UTC12h 15m
2026-07-07 UAL809 SFO → MNL Jul 7, 21:53 UTCJul 8, 10:38 UTC12h 45m
2026-07-07 UAL809 - Jul 7, 21:50 UTCJul 8, 10:45 UTC12h 55m
2026-07-07 UAL1960 - Jul 7, 11:20 UTCJul 7, 16:35 UTC5h 15m
2026-07-06 UAL43 - Jul 6, 13:10 UTCJul 6, 21:05 UTC7h 55m
2026-07-06 UAL43 FRA → EWR Jul 6, 13:06 UTCJul 6, 20:59 UTC7h 53m
2026-07-06 UAL42 EWR → FRA Jul 6, 04:00 UTCJul 6, 10:35 UTC6h 35m
2026-07-05 UAL78 NRT → EWR Jul 5, 10:10 UTCJul 5, 10:40 UTC30m
2026-07-05 UAL78 NRT → EWR Jul 5, 10:11 UTCJul 5, 21:51 UTC11h 40m
2026-07-04 UAL79 - Jul 4, 19:30 UTCJul 5, 07:45 UTC12h 15m
2026-07-03 UAL78 NRT → EWR Jul 3, 08:50 UTCJul 3, 21:10 UTC12h 20m
2026-07-02 UAL837 SFO → NRT Jul 2, 20:10 UTCJul 3, 06:15 UTC10h 5m

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 N2333U page for operator, model, and routing details .

Mode-S A21679 frequently asked

What is Mode-S code A21679?
A21679 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N2333U.
Where is Mode-S A21679 registered?
Mode-S code A21679 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 A21679 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 10:25 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A21679, octal 50413171, decimal 10,622,585.
What flights does A21679 operate?
Mode-S A21679 has broadcast 20 distinct callsigns, including UAL1175, UAL43, UAL809, UAL862, UAL950.