sensors Mode-S transponder
A31A50
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N29971 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A31A50
- Octal
- 50615120
- Decimal
- 10,689,104
- Country
- US
- Tail
- N29971
- Type
- B789
- Flights observed
- 194
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 6h ago
Last known position
Country allocation
The ICAO 24-bit address A31A50 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 |
|---|---|---|---|
| UAL27 | - | 8 | 2026-06-25 |
| UAL262 | - | 8 | 2026-06-29 |
| UAL153 | United Airlines | 8 | 2026-05-30 |
| UAL33 | - | 7 | 2026-07-05 |
| UAL152 | United Airlines | 7 | 2026-05-29 |
| UAL32 | United Airlines | 6 | 2026-06-01 |
| UAL263 | - | 6 | 2026-06-29 |
| UAL26 | - | 6 | 2026-06-26 |
| UAL935 | United Airlines | 5 | 2026-05-31 |
| UAL79 | United Airlines | 5 | 2026-04-30 |
| UAL923 | - | 4 | 2026-07-05 |
| UAL892 | - | 4 | 2026-06-22 |
| UAL805 | - | 4 | 2026-06-19 |
| UAL62 | - | 4 | 2026-07-03 |
| UAL61 | United Airlines | 4 | 2026-04-28 |
| UAL2222 | - | 4 | 2026-07-11 |
| UAL1855 | United Airlines | 4 | 2026-05-17 |
| UAL182 | United Airlines | 4 | 2026-06-03 |
| UAL181 | United Airlines | 4 | 2026-06-04 |
| UAL178 | United Airlines | 4 | 2026-06-27 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-14 | UAL820 | - | Jul 14, 02:15 UTC | Jul 14, 02:30 UTC | 15m |
| 2026-07-14 | UAL820 | - | Jul 14, 00:20 UTC | Jul 14, 00:30 UTC | 10m |
| 2026-07-13 | UAL820 | - | Jul 13, 07:40 UTC | Jul 13, 21:25 UTC | 13h 45m |
| 2026-07-12 | UAL353 | - | Jul 12, 23:10 UTC | Jul 13, 03:50 UTC | 4h 40m |
| 2026-07-11 | UAL2222 | CPT → EWR | Jul 11, 18:12 UTC | Jul 12, 08:29 UTC | 14h 17m |
| 2026-07-11 | UAL2222 | - | Jul 11, 17:55 UTC | Jul 12, 08:30 UTC | 14h 35m |
| 2026-07-11 | UAL1122 | - | Jul 11, 15:00 UTC | Jul 11, 15:15 UTC | 15m |
| 2026-07-11 | UAL1122 | - | Jul 11, 01:20 UTC | Jul 11, 01:55 UTC | 35m |
| 2026-07-09 | UAL83 | DEL → EWR | Jul 9, 18:35 UTC | Jul 9, 19:15 UTC | 40m |
| 2026-07-09 | UAL83 | DEL → EWR | Jul 9, 18:37 UTC | Jul 10, 10:22 UTC | 15h 45m |
| 2026-07-09 | UAL82 | - | Jul 9, 02:10 UTC | Jul 9, 16:05 UTC | 13h 55m |
| 2026-07-08 | UAL2096 | LAX → EWR | Jul 8, 15:45 UTC | Jul 8, 20:15 UTC | 4h 30m |
| 2026-07-08 | UAL842 | SYD → LAX | Jul 8, 00:06 UTC | Jul 8, 12:44 UTC | 12h 38m |
| 2026-07-08 | UAL842 | - | Jul 8, 00:05 UTC | Jul 8, 12:45 UTC | 12h 40m |
| 2026-07-07 | UAL863 | SFO → SYD | Jul 7, 06:38 UTC | Jul 7, 21:02 UTC | 14h 24m |
| 2026-07-07 | UAL863 | SFO → SYD | Jul 7, 06:35 UTC | Jul 7, 21:00 UTC | 14h 25m |
| 2026-07-06 | UAL949 | - | Jul 6, 12:30 UTC | Jul 6, 15:00 UTC | 2h 30m |
| 2026-07-06 | UAL949 | LHR → SFO | Jul 6, 12:25 UTC | Jul 6, 22:47 UTC | 10h 22m |
| 2026-07-05 | UAL923 | - | Jul 5, 23:05 UTC | Jul 6, 09:00 UTC | 9h 55m |
| 2026-07-05 | UAL33 | - | Jul 5, 08:00 UTC | Jul 5, 17:35 UTC | 9h 35m |
| 2026-07-05 | UAL33 | NRT → LAX | Jul 5, 08:05 UTC | Jul 5, 17:29 UTC | 9h 24m |
| 2026-07-04 | UAL7 | - | Jul 4, 15:45 UTC | Jul 5, 04:30 UTC | 12h 45m |
| 2026-07-04 | UAL63 | - | Jul 4, 01:10 UTC | Jul 4, 10:35 UTC | 9h 25m |
| 2026-07-03 | UAL62 | - | Jul 3, 00:05 UTC | Jul 3, 09:30 UTC | 9h 25m |
| 2026-07-02 | UAL6 | - | Jul 2, 08:25 UTC | Jul 2, 19:20 UTC | 10h 55m |
| 2026-07-01 | UAL143 | DEN → NRT | Jul 1, 18:00 UTC | Jul 2, 05:05 UTC | 11h 5m |
| 2026-06-30 | UAL761 | MUC → DEN | Jun 30, 14:40 UTC | Jul 1, 00:55 UTC | 10h 15m |
| 2026-06-30 | UAL760 | DEN → MUC | Jun 30, 02:50 UTC | Jun 30, 12:00 UTC | 9h 10m |
| 2026-06-29 | UAL263 | - | Jun 29, 14:29 UTC | Jun 29, 23:39 UTC | 9h 10m |
| 2026-06-29 | UAL263 | LHR → DEN | Jun 29, 14:14 UTC | Jun 29, 23:32 UTC | 9h 18m |
| 2026-06-29 | UAL262 | DEN → LHR | Jun 29, 03:14 UTC | Jun 29, 11:29 UTC | 8h 15m |
| 2026-06-28 | UAL263 | - | Jun 28, 14:14 UTC | Jun 28, 23:09 UTC | 8h 55m |
| 2026-06-28 | UAL262 | DEN → LHR | Jun 28, 02:55 UTC | Jun 28, 11:14 UTC | 8h 19m |
| 2026-06-28 | UAL262 | DEN → LHR | Jun 28, 03:00 UTC | Jun 28, 11:25 UTC | 8h 25m |
| 2026-06-27 | UAL178 | KIX → GUM | Jun 27, 12:39 UTC | Jun 27, 23:34 UTC | 10h 55m |
| 2026-06-27 | UAL177 | DEN → FCO | Jun 27, 00:14 UTC | Jun 27, 10:19 UTC | 10h 5m |
| 2026-06-26 | UAL26 | - | Jun 26, 10:55 UTC | Jun 26, 19:39 UTC | 8h 45m |
| 2026-06-25 | UAL27 | DEN → LHR | Jun 25, 23:58 UTC | Jun 26, 08:16 UTC | 8h 18m |
| 2026-06-25 | UAL27 | DEN → LHR | Jun 25, 23:55 UTC | Jun 26, 08:20 UTC | 8h 25m |
| 2026-06-25 | UAL26 | - | Jun 25, 11:04 UTC | Jun 25, 19:59 UTC | 8h 55m |
| 2026-06-24 | UAL27 | DEN → LHR | Jun 24, 23:54 UTC | Jun 25, 08:34 UTC | 8h 40m |
| 2026-06-24 | UAL27 | DEN → LHR | Jun 24, 23:58 UTC | Jun 25, 08:28 UTC | 8h 30m |
| 2026-06-24 | UAL142 | NRT → DEN | Jun 24, 08:30 UTC | Jun 24, 18:29 UTC | 10h 0m |
| 2026-06-24 | UAL142 | NRT → DEN | Jun 24, 08:05 UTC | Jun 24, 18:31 UTC | 10h 26m |
| 2026-06-23 | UAL143 | DEN → NRT | Jun 23, 18:55 UTC | Jun 24, 05:49 UTC | 10h 55m |
| 2026-06-23 | UAL3924 | - | Jun 23, 14:55 UTC | Jun 23, 16:50 UTC | 1h 55m |
| 2026-06-22 | UAL892 | - | Jun 22, 08:10 UTC | Jun 22, 18:04 UTC | 9h 55m |
| 2026-06-21 | UAL893 | SFO → ICN | Jun 21, 18:20 UTC | Jun 22, 05:44 UTC | 11h 25m |
| 2026-06-21 | UAL114 | - | Jun 21, 07:20 UTC | Jun 21, 14:59 UTC | 7h 40m |
| 2026-06-20 | UAL115 | SFO → PPT | Jun 20, 21:14 UTC | Jun 21, 05:04 UTC | 7h 50m |
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 N29971 page for operator, model, and routing details .