sensors Mode-S transponder
A31A56
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N29977 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A31A56
- Octal
- 50615126
- Decimal
- 10,689,110
- Country
- US
- Tail
- N29977
- Type
- B789
- Flights observed
- 91
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 1d ago
Last known position
Country allocation
The ICAO 24-bit address A31A56 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 |
|---|---|---|---|
| UAL805 | United Airlines | 7 | 2026-05-14 |
| UAL839 | United Airlines | 6 | 2026-05-27 |
| UAL152 | United Airlines | 6 | 2026-05-23 |
| UAL821 | United Airlines | 5 | 2026-04-30 |
| UAL153 | United Airlines | 5 | 2026-05-24 |
| UAL842 | United Airlines | 4 | 2026-05-27 |
| UAL83 | United Airlines | 4 | 2026-05-19 |
| UAL820 | United Airlines | 4 | 2026-04-30 |
| UAL806 | United Airlines | 4 | 2026-05-15 |
| UAL2692 | United Airlines | 4 | 2026-04-14 |
| UAL199 | United Airlines | 4 | 2026-04-28 |
| UAL188 | United Airlines | 4 | 2026-04-13 |
| UAL187 | United Airlines | 3 | 2026-04-14 |
| UAL1849 | United Airlines | 3 | 2026-05-15 |
| UAL1757 | United Airlines | 3 | 2026-05-15 |
| UAL115 | United Airlines | 3 | 2026-05-17 |
| UAL892 | United Airlines | 2 | 2026-05-13 |
| UAL82 | United Airlines | 2 | 2026-05-19 |
| UAL79 | United Airlines | 2 | 2026-05-20 |
| UAL33 | United Airlines | 2 | 2026-05-21 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-05-27 | UAL842 | SYD → LAX | May 27, 23:50 UTC | May 28, 13:00 UTC | 13h 10m |
| 2026-05-27 | UAL839 | LAX → SYD | May 27, 06:29 UTC | May 27, 20:50 UTC | 14h 20m |
| 2026-05-27 | UAL839 | LAX → SYD | May 27, 06:09 UTC | May 27, 20:42 UTC | 14h 33m |
| 2026-05-24 | UAL153 | HKG → LAX | May 24, 04:50 UTC | May 24, 17:55 UTC | 13h 5m |
| 2026-05-24 | UAL153 | HKG → LAX | May 24, 02:00 UTC | May 24, 02:20 UTC | 20m |
| 2026-05-24 | UAL153 | HKG → LAX | May 24, 00:19 UTC | May 24, 02:18 UTC | 1h 59m |
| 2026-05-23 | UAL152 | LAX → HKG | May 23, 16:40 UTC | May 23, 16:50 UTC | 10m |
| 2026-05-22 | UAL152 | LAX → HKG | May 22, 20:10 UTC | May 23, 10:20 UTC | 14h 9m |
| 2026-05-21 | UAL33 | NRT → LAX | May 21, 08:00 UTC | May 21, 17:45 UTC | 9h 45m |
| 2026-05-21 | UAL33 | NRT → LAX | May 21, 08:05 UTC | May 21, 17:36 UTC | 9h 31m |
| 2026-05-20 | UAL79 | EWR → NRT | May 20, 15:47 UTC | May 21, 04:59 UTC | 13h 12m |
| 2026-05-20 | UAL79 | EWR → NRT | May 20, 15:50 UTC | May 20, 23:00 UTC | 7h 10m |
| 2026-05-19 | UAL83 | DEL → EWR | May 19, 18:25 UTC | May 20, 09:35 UTC | 15h 11m |
| 2026-05-19 | UAL83 | DEL → EWR | May 19, 18:32 UTC | May 20, 09:32 UTC | 15h 0m |
| 2026-05-19 | UAL82 | EWR → DEL | May 19, 01:30 UTC | May 19, 15:40 UTC | 14h 10m |
| 2026-05-18 | UAL713 | ORD → DEL | May 18, 17:50 UTC | May 18, 22:50 UTC | 4h 59m |
| 2026-05-18 | UAL114 | PPT → SFO | May 18, 07:15 UTC | May 18, 15:35 UTC | 8h 20m |
| 2026-05-17 | UAL115 | SFO → PPT | May 17, 20:55 UTC | May 18, 05:00 UTC | 8h 5m |
| 2026-05-17 | UAL114 | PPT → SFO | May 17, 09:45 UTC | May 17, 17:45 UTC | 8h 0m |
| 2026-05-17 | UAL115 | SFO → PPT | May 17, 00:07 UTC | May 17, 07:31 UTC | 7h 24m |
| 2026-05-17 | UAL115 | SFO → PPT | May 17, 00:00 UTC | May 17, 07:20 UTC | 7h 20m |
| 2026-05-15 | UAL1757 | PIT → DEN | May 15, 22:30 UTC | May 16, 03:30 UTC | 5h 0m |
| 2026-05-15 | UAL1849 | MCO → EWR | May 15, 15:35 UTC | May 15, 19:55 UTC | 4h 20m |
| 2026-05-15 | UAL806 | ICN → SFO | May 15, 02:45 UTC | May 15, 13:10 UTC | 10h 25m |
| 2026-05-14 | UAL805 | SFO → ICN | May 14, 07:17 UTC | May 14, 18:25 UTC | 11h 8m |
| 2026-05-14 | UAL805 | SFO → ICN | May 14, 07:25 UTC | May 14, 18:30 UTC | 11h 5m |
| 2026-05-13 | UAL892 | ICN → SFO | May 13, 08:16 UTC | May 13, 17:58 UTC | 9h 42m |
| 2026-05-13 | UAL892 | ICN → SFO | May 13, 07:55 UTC | May 13, 18:05 UTC | 10h 10m |
| 2026-05-12 | UAL893 | SFO → ICN | May 12, 17:55 UTC | May 13, 05:15 UTC | 11h 20m |
| 2026-05-12 | UAL806 | ICN → SFO | May 12, 02:45 UTC | May 12, 12:50 UTC | 10h 5m |
| 2026-05-11 | UAL805 | SFO → ICN | May 11, 07:20 UTC | May 11, 18:35 UTC | 11h 15m |
| 2026-05-10 | UAL1757 | PIT → DEN | May 10, 22:35 UTC | May 11, 03:45 UTC | 5h 10m |
| 2026-05-10 | UAL1849 | MCO → EWR | May 10, 15:45 UTC | May 10, 20:09 UTC | 4h 25m |
| 2026-05-10 | UAL806 | ICN → SFO | May 10, 02:45 UTC | May 10, 12:54 UTC | 10h 10m |
| 2026-05-09 | UAL805 | SFO → ICN | May 9, 17:35 UTC | May 9, 20:00 UTC | 2h 25m |
| 2026-05-09 | UAL805 | SFO → ICN | May 9, 07:30 UTC | May 9, 07:55 UTC | 25m |
| 2026-05-08 | UAL1757 | PIT → DEN | May 8, 22:30 UTC | May 9, 03:50 UTC | 5h 20m |
| 2026-05-08 | UAL1849 | MCO → EWR | May 8, 15:25 UTC | May 8, 19:50 UTC | 4h 25m |
| 2026-05-07 | UAL806 | ICN → SFO | May 7, 02:40 UTC | May 7, 13:00 UTC | 10h 20m |
| 2026-05-06 | UAL805 | SFO → ICN | May 6, 07:11 UTC | May 6, 18:47 UTC | 11h 36m |
| 2026-05-06 | UAL805 | SFO → ICN | May 6, 07:05 UTC | May 6, 17:25 UTC | 10h 20m |
| 2026-05-05 | UAL1227 | PHX → IAD | May 5, 17:55 UTC | May 5, 23:30 UTC | 5h 35m |
| 2026-05-05 | UAL123 | ANC → ORD | May 5, 07:00 UTC | May 5, 13:55 UTC | 6h 55m |
| 2026-05-04 | UAL122 | IAD → LHR | May 4, 14:19 UTC | May 4, 20:20 UTC | 6h 1m |
| 2026-05-04 | UAL122 | IAD → LHR | May 4, 14:05 UTC | May 4, 20:20 UTC | 6h 16m |
| 2026-05-03 | UAL83 | DEL → EWR | May 3, 19:45 UTC | May 3, 20:20 UTC | 35m |
| 2026-05-03 | UAL83 | DEL → EWR | May 3, 18:32 UTC | May 4, 11:06 UTC | 16h 34m |
| 2026-05-03 | UAL82 | EWR → DEL | May 3, 01:40 UTC | May 3, 16:00 UTC | 14h 19m |
| 2026-05-02 | UAL78 | NRT → EWR | May 2, 08:45 UTC | May 2, 20:55 UTC | 12h 10m |
| 2026-05-01 | UAL32 | LAX → NRT | May 1, 18:05 UTC | May 2, 05:10 UTC | 11h 6m |
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 N29977 page for operator, model, and routing details .