sensors Mode-S transponder
A6679B
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N51104 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC.
- Hex
- A6679B
- Octal
- 51463633
- Decimal
- 10,905,499
- Country
- US
- Tail
- N51104
- Type
- B789
- Flights observed
- 85
- Distinct callsigns
- 14
- Country
- US
- Last broadcast
- 3h ago
Last known position
Country allocation
The ICAO 24-bit address A6679B 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 14 distinct
| Callsign | Airline | Flights | Last seen |
|---|---|---|---|
| UAL1 | United Airlines | 21 | 2026-05-29 |
| UAL2 | United Airlines | 17 | 2026-05-30 |
| UAL901 | United Airlines | 7 | 2026-05-25 |
| UAL900 | United Airlines | 7 | 2026-05-26 |
| UAL755 | United Airlines | 7 | 2026-04-17 |
| UAL2498 | United Airlines | 7 | 2026-04-27 |
| UAL382 | United Airlines | 6 | 2026-04-27 |
| UAL1434 | United Airlines | 5 | 2026-04-18 |
| UAL930 | United Airlines | 3 | 2026-05-28 |
| UAL939 | United Airlines | 1 | 2026-05-28 |
| UAL505 | United Airlines | 1 | 2026-04-30 |
| UAL3974 | United Airlines | 1 | 2026-05-14 |
| UAL3932 | United Airlines | 1 | 2026-05-14 |
| UAL1768 | United Airlines | 1 | 2026-04-30 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-05-30 | UAL2 | SIN → SFO | May 30, 04:25 UTC | May 30, 04:45 UTC | 20m |
| 2026-05-29 | UAL1 | SFO → SIN | May 29, 06:21 UTC | May 29, 22:32 UTC | 16h 11m |
| 2026-05-29 | UAL1 | SFO → SIN | May 29, 06:40 UTC | May 29, 20:50 UTC | 14h 10m |
| 2026-05-28 | UAL939 | LHR → SFO | May 28, 15:55 UTC | May 29, 01:45 UTC | 9h 50m |
| 2026-05-28 | UAL930 | SFO → LHR | May 28, 13:15 UTC | May 28, 13:25 UTC | 10m |
| 2026-05-28 | UAL930 | SFO → LHR | May 28, 03:29 UTC | May 28, 13:00 UTC | 9h 31m |
| 2026-05-28 | UAL930 | SFO → LHR | May 28, 03:20 UTC | May 28, 06:10 UTC | 2h 50m |
| 2026-05-26 | UAL900 | LHR → SFO | May 26, 10:05 UTC | May 26, 20:24 UTC | 10h 20m |
| 2026-05-25 | UAL901 | SFO → LHR | May 25, 20:40 UTC | May 26, 06:29 UTC | 9h 50m |
| 2026-05-25 | UAL2 | SIN → SFO | May 25, 01:16 UTC | May 25, 16:16 UTC | 15h 0m |
| 2026-05-24 | UAL2 | SIN → SFO | May 24, 19:00 UTC | May 25, 16:30 UTC | 21h 30m |
| 2026-05-24 | UAL1 | SFO → SIN | May 24, 06:50 UTC | May 25, 04:20 UTC | 21h 30m |
| 2026-05-24 | UAL1 | SFO → SIN | May 24, 06:40 UTC | May 25, 04:20 UTC | 21h 40m |
| 2026-05-23 | UAL2 | SIN → SFO | May 23, 01:16 UTC | May 23, 15:38 UTC | 14h 22m |
| 2026-05-23 | UAL2 | SIN → SFO | May 23, 02:30 UTC | May 23, 15:30 UTC | 13h 0m |
| 2026-05-22 | UAL1 | SFO → SIN | May 22, 06:21 UTC | May 22, 21:58 UTC | 15h 37m |
| 2026-05-22 | UAL1 | SFO → SIN | May 22, 06:25 UTC | May 22, 18:45 UTC | 12h 20m |
| 2026-05-21 | UAL900 | LHR → SFO | May 21, 09:55 UTC | May 21, 12:10 UTC | 2h 15m |
| 2026-05-21 | UAL900 | LHR → SFO | May 21, 10:00 UTC | May 21, 19:45 UTC | 9h 45m |
| 2026-05-20 | UAL901 | SFO → LHR | May 20, 20:26 UTC | May 21, 05:58 UTC | 9h 32m |
| 2026-05-20 | UAL901 | SFO → LHR | May 20, 20:25 UTC | May 21, 06:00 UTC | 9h 35m |
| 2026-05-19 | UAL2 | SIN → SFO | May 19, 02:50 UTC | May 19, 07:35 UTC | 4h 45m |
| 2026-05-19 | UAL2 | SIN → SFO | May 19, 01:31 UTC | May 19, 15:35 UTC | 14h 4m |
| 2026-05-18 | UAL1 | SFO → SIN | May 18, 06:31 UTC | May 18, 22:45 UTC | 16h 14m |
| 2026-05-18 | UAL1 | SFO → SIN | May 18, 06:35 UTC | May 18, 20:15 UTC | 13h 39m |
| 2026-05-17 | UAL2 | SIN → SFO | May 17, 01:31 UTC | May 17, 15:19 UTC | 13h 48m |
| 2026-05-16 | UAL1 | SFO → SIN | May 16, 06:26 UTC | May 16, 22:36 UTC | 16h 10m |
| 2026-05-16 | UAL1 | SFO → SIN | May 16, 06:41 UTC | May 16, 20:45 UTC | 14h 5m |
| 2026-05-14 | UAL3932 | EWR → IAD | May 14, 21:50 UTC | May 15, 02:20 UTC | 4h 30m |
| 2026-05-14 | UAL3974 | SIN → HNL | May 14, 08:10 UTC | May 14, 18:55 UTC | 10h 45m |
| 2026-05-10 | UAL1 | SFO → SIN | May 10, 06:11 UTC | May 10, 22:15 UTC | 16h 4m |
| 2026-05-10 | UAL1 | SFO → SIN | May 10, 06:04 UTC | May 10, 20:45 UTC | 14h 40m |
| 2026-05-09 | UAL900 | LHR → SFO | May 9, 10:05 UTC | May 9, 20:15 UTC | 10h 10m |
| 2026-05-08 | UAL901 | SFO → LHR | May 8, 20:17 UTC | May 9, 06:08 UTC | 9h 51m |
| 2026-05-08 | UAL901 | SFO → LHR | May 8, 20:25 UTC | May 9, 06:20 UTC | 9h 55m |
| 2026-05-08 | UAL2 | SIN → SFO | May 8, 02:49 UTC | May 8, 04:25 UTC | 1h 35m |
| 2026-05-07 | UAL2 | SIN → SFO | May 7, 20:50 UTC | May 8, 15:45 UTC | 18h 55m |
| 2026-05-07 | UAL2 | SIN → SFO | May 7, 20:30 UTC | May 8, 15:45 UTC | 19h 15m |
| 2026-05-07 | UAL1 | SFO → SIN | May 7, 06:11 UTC | May 7, 22:26 UTC | 16h 15m |
| 2026-05-07 | UAL1 | SFO → SIN | May 7, 06:15 UTC | May 7, 21:05 UTC | 14h 50m |
| 2026-05-06 | UAL900 | LHR → SFO | May 6, 09:55 UTC | May 6, 20:10 UTC | 10h 14m |
| 2026-05-05 | UAL901 | SFO → LHR | May 5, 20:25 UTC | May 6, 06:30 UTC | 10h 5m |
| 2026-05-04 | UAL2 | SIN → SFO | May 4, 20:50 UTC | May 5, 16:00 UTC | 19h 10m |
| 2026-05-04 | UAL2 | SIN → SFO | May 4, 20:40 UTC | May 5, 16:00 UTC | 19h 20m |
| 2026-05-04 | UAL1 | SFO → SIN | May 4, 06:25 UTC | May 5, 04:30 UTC | 22h 6m |
| 2026-05-03 | UAL900 | LHR → SFO | May 3, 09:50 UTC | May 3, 10:45 UTC | 55m |
| 2026-05-03 | UAL900 | LHR → SFO | May 3, 10:00 UTC | May 3, 20:03 UTC | 10h 3m |
| 2026-05-02 | UAL901 | SFO → LHR | May 2, 20:35 UTC | May 3, 06:25 UTC | 9h 49m |
| 2026-05-02 | UAL2 | SIN → SFO | May 2, 02:50 UTC | May 2, 16:10 UTC | 13h 20m |
| 2026-05-02 | UAL2 | SIN → SFO | May 2, 01:31 UTC | May 2, 16:11 UTC | 14h 40m |
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 N51104 page for operator, model, and routing details .