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
- Flights observed
- 112
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 9h ago
Last known position
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 | United Airlines | 11 | 2026-05-29 |
| UAL809 | United Airlines | 8 | 2026-05-24 |
| UAL201 | United Airlines | 8 | 2026-05-30 |
| UAL810 | United Airlines | 6 | 2026-05-25 |
| UAL878 | United Airlines | 5 | 2026-05-27 |
| UAL871 | United Airlines | 5 | 2026-05-22 |
| UAL869 | United Airlines | 5 | 2026-05-26 |
| UAL43 | United Airlines | 5 | 2026-05-18 |
| UAL42 | United Airlines | 5 | 2026-05-17 |
| UAL200 | United Airlines | 5 | 2026-05-17 |
| UAL1411 | United Airlines | 5 | 2026-05-17 |
| UAL872 | United Airlines | 4 | 2026-05-24 |
| UAL190 | United Airlines | 4 | 2026-05-29 |
| UAL189 | United Airlines | 4 | 2026-05-28 |
| UAL950 | United Airlines | 3 | 2026-05-02 |
| UAL2328 | United Airlines | 3 | 2026-05-08 |
| UAL1149 | United Airlines | 3 | 2026-05-17 |
| UAL989 | United Airlines | 2 | 2026-05-03 |
| UAL988 | United Airlines | 2 | 2026-05-02 |
| UAL951 | United Airlines | 2 | 2026-05-03 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-05-30 | UAL201 | HNL → GUM | May 30, 01:00 UTC | May 30, 01:15 UTC | 15m |
| 2026-05-29 | UAL1175 | SFO → HNL | May 29, 21:15 UTC | May 29, 21:25 UTC | 10m |
| 2026-05-29 | UAL1175 | SFO → HNL | May 29, 16:45 UTC | May 29, 17:10 UTC | 25m |
| 2026-05-29 | UAL190 | IAH → MIA | May 29, 01:05 UTC | May 29, 13:30 UTC | 12h 25m |
| 2026-05-29 | UAL190 | IAH → MIA | May 29, 01:01 UTC | May 29, 13:25 UTC | 12h 24m |
| 2026-05-28 | UAL189 | CLE → PHX | May 28, 08:19 UTC | May 28, 21:34 UTC | 13h 15m |
| 2026-05-28 | UAL189 | CLE → PHX | May 28, 08:10 UTC | May 28, 08:35 UTC | 25m |
| 2026-05-27 | UAL878 | HKG → SFO | May 27, 14:51 UTC | May 28, 03:17 UTC | 12h 26m |
| 2026-05-27 | UAL878 | HKG → SFO | May 27, 14:50 UTC | May 28, 03:30 UTC | 12h 40m |
| 2026-05-26 | UAL869 | SFO → HKG | May 26, 21:34 UTC | May 27, 11:05 UTC | 13h 31m |
| 2026-05-25 | UAL810 | PHL → DEN | May 25, 13:40 UTC | May 26, 01:49 UTC | 12h 9m |
| 2026-05-24 | UAL809 | SEA → IAD | May 24, 21:43 UTC | May 25, 10:42 UTC | 12h 59m |
| 2026-05-24 | UAL809 | SEA → IAD | May 24, 21:40 UTC | May 24, 21:50 UTC | 10m |
| 2026-05-24 | UAL872 | TPE → SFO | May 24, 02:23 UTC | May 24, 13:10 UTC | 10h 47m |
| 2026-05-24 | UAL872 | TPE → SFO | May 24, 02:05 UTC | May 24, 13:10 UTC | 11h 5m |
| 2026-05-22 | UAL871 | SFO → TPE | May 22, 22:28 UTC | May 23, 11:05 UTC | 12h 37m |
| 2026-05-22 | UAL871 | SFO → TPE | May 22, 22:35 UTC | May 22, 22:55 UTC | 20m |
| 2026-05-22 | UAL862 | HKG → SFO | May 22, 04:11 UTC | May 22, 16:10 UTC | 11h 59m |
| 2026-05-22 | UAL862 | HKG → SFO | May 22, 04:00 UTC | May 22, 07:35 UTC | 3h 35m |
| 2026-05-21 | UAL877 | SFO → HKG | May 21, 06:30 UTC | May 21, 20:00 UTC | 13h 30m |
| 2026-05-20 | UAL878 | HKG → SFO | May 20, 14:51 UTC | May 21, 02:45 UTC | 11h 54m |
| 2026-05-20 | UAL878 | HKG → SFO | May 20, 14:35 UTC | May 21, 02:15 UTC | 11h 40m |
| 2026-05-20 | UAL869 | SFO → HKG | May 20, 10:20 UTC | May 20, 10:40 UTC | 20m |
| 2026-05-19 | UAL869 | SFO → HKG | May 19, 20:40 UTC | May 20, 09:50 UTC | 13h 11m |
| 2026-05-19 | UAL1960 | MCO → ORD | May 19, 11:20 UTC | May 19, 17:00 UTC | 5h 40m |
| 2026-05-18 | UAL43 | OGG → EWR | May 18, 09:40 UTC | May 18, 17:20 UTC | 7h 40m |
| 2026-05-17 | UAL42 | OGG → EWR | May 17, 23:50 UTC | May 18, 06:47 UTC | 6h 57m |
| 2026-05-17 | UAL42 | OGG → EWR | May 17, 23:55 UTC | May 18, 01:35 UTC | 1h 40m |
| 2026-05-17 | UAL1149 | EWR → SRQ | May 17, 14:35 UTC | May 17, 19:55 UTC | 5h 20m |
| 2026-05-17 | UAL1411 | SFO → EWR | May 17, 11:55 UTC | May 17, 12:30 UTC | 35m |
| 2026-05-17 | UAL1411 | SFO → EWR | May 17, 07:45 UTC | May 17, 07:55 UTC | 10m |
| 2026-05-17 | UAL200 | GUM → HNL | May 17, 03:55 UTC | May 17, 04:15 UTC | 20m |
| 2026-05-16 | UAL200 | GUM → HNL | May 16, 21:23 UTC | May 17, 04:15 UTC | 6h 52m |
| 2026-05-16 | UAL201 | HNL → GUM | May 16, 01:40 UTC | May 16, 02:15 UTC | 35m |
| 2026-05-16 | UAL201 | HNL → GUM | May 16, 01:19 UTC | May 16, 08:50 UTC | 7h 31m |
| 2026-05-15 | UAL1175 | SFO → HNL | May 15, 21:40 UTC | May 15, 22:00 UTC | 20m |
| 2026-05-15 | UAL1175 | SFO → HNL | May 15, 17:10 UTC | May 15, 17:35 UTC | 25m |
| 2026-05-15 | UAL1175 | SFO → HNL | May 15, 16:43 UTC | May 15, 22:04 UTC | 5h 21m |
| 2026-05-15 | UAL190 | IAH → MIA | May 15, 01:05 UTC | May 15, 12:25 UTC | 11h 20m |
| 2026-05-15 | UAL190 | IAH → MIA | May 15, 01:01 UTC | May 15, 12:20 UTC | 11h 19m |
| 2026-05-14 | UAL189 | CLE → PHX | May 14, 07:54 UTC | May 14, 21:50 UTC | 13h 56m |
| 2026-05-14 | UAL189 | CLE → PHX | May 14, 07:50 UTC | May 14, 22:00 UTC | 14h 10m |
| 2026-05-12 | UAL878 | HKG → SFO | May 12, 15:01 UTC | May 13, 02:55 UTC | 11h 55m |
| 2026-05-12 | UAL869 | SFO → HKG | May 12, 10:20 UTC | May 12, 10:35 UTC | 15m |
| 2026-05-11 | UAL869 | SFO → HKG | May 11, 20:55 UTC | May 12, 09:45 UTC | 12h 50m |
| 2026-05-11 | UAL1411 | SFO → EWR | May 11, 07:50 UTC | May 11, 12:20 UTC | 4h 30m |
| 2026-05-11 | UAL200 | GUM → HNL | May 11, 03:35 UTC | May 11, 04:00 UTC | 25m |
| 2026-05-10 | UAL201 | HNL → GUM | May 10, 00:34 UTC | May 10, 01:00 UTC | 25m |
| 2026-05-10 | UAL201 | HNL → GUM | May 10, 00:39 UTC | May 10, 07:54 UTC | 7h 15m |
| 2026-05-09 | UAL1175 | SFO → HNL | May 9, 21:19 UTC | May 9, 21:34 UTC | 15m |
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 .