sensors Mode-S transponder
A31A73
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N29981 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A31A73
- Octal
- 50615163
- Decimal
- 10,689,139
- Country
- US
- Tail
- N29981
- Type
- B789
- Flights observed
- 174
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 10h ago
Last known position
Country allocation
The ICAO 24-bit address A31A73 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 |
|---|---|---|---|
| UAL152 | United Airlines | 22 | 2026-07-01 |
| UAL153 | United Airlines | 21 | 2026-07-02 |
| UAL198 | United Airlines | 10 | 2026-06-07 |
| UAL842 | - | 7 | 2026-06-30 |
| UAL199 | United Airlines | 7 | 2026-06-07 |
| UAL2303 | - | 5 | 2026-06-17 |
| UAL187 | - | 5 | 2026-06-15 |
| UAL1855 | - | 5 | 2026-07-03 |
| UAL923 | - | 4 | 2026-06-27 |
| UAL863 | - | 4 | 2026-06-29 |
| UAL82 | - | 4 | 2026-07-12 |
| UAL33 | - | 4 | 2026-06-23 |
| UAL32 | - | 4 | 2026-06-19 |
| UAL2403 | - | 4 | 2026-06-17 |
| UAL2222 | United Airlines | 4 | 2026-05-23 |
| UAL1227 | - | 4 | 2026-07-07 |
| UAL1122 | United Airlines | 4 | 2026-05-23 |
| UAL935 | - | 3 | 2026-06-18 |
| UAL839 | United Airlines | 3 | 2026-05-30 |
| UAL83 | - | 3 | 2026-07-12 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-13 | UAL122 | EWR → LHR | Jul 13, 14:19 UTC | Jul 13, 20:19 UTC | 6h 0m |
| 2026-07-13 | UAL122 | - | Jul 13, 14:00 UTC | Jul 13, 20:20 UTC | 6h 20m |
| 2026-07-12 | UAL83 | - | Jul 12, 18:45 UTC | Jul 13, 09:55 UTC | 15h 10m |
| 2026-07-12 | UAL82 | - | Jul 12, 02:45 UTC | Jul 12, 04:15 UTC | 1h 30m |
| 2026-07-12 | UAL82 | EWR → DEL | Jul 12, 02:19 UTC | Jul 12, 16:32 UTC | 14h 13m |
| 2026-07-11 | UAL83 | FRA → EWR | Jul 11, 07:15 UTC | Jul 11, 15:10 UTC | 7h 55m |
| 2026-07-10 | UAL83 | - | Jul 10, 21:15 UTC | Jul 11, 05:31 UTC | 8h 15m |
| 2026-07-10 | UAL82 | EWR → DEL | Jul 10, 02:24 UTC | Jul 10, 16:14 UTC | 13h 50m |
| 2026-07-10 | UAL82 | - | Jul 10, 02:25 UTC | Jul 10, 16:05 UTC | 13h 40m |
| 2026-07-09 | UAL713 | SFO → EWR | Jul 9, 18:55 UTC | Jul 9, 23:45 UTC | 4h 50m |
| 2026-07-09 | UAL61 | - | Jul 9, 01:05 UTC | Jul 9, 14:30 UTC | 13h 25m |
| 2026-07-08 | UAL60 | SFO → MEL | Jul 8, 07:10 UTC | Jul 8, 22:05 UTC | 14h 55m |
| 2026-07-07 | UAL1227 | EWR → SFO | Jul 7, 17:50 UTC | Jul 7, 23:00 UTC | 5h 10m |
| 2026-07-07 | UAL123 | - | Jul 7, 13:10 UTC | Jul 7, 14:45 UTC | 1h 35m |
| 2026-07-07 | UAL123 | - | Jul 7, 07:55 UTC | Jul 7, 13:05 UTC | 5h 10m |
| 2026-07-06 | UAL122 | EWR → LHR | Jul 6, 14:15 UTC | Jul 6, 20:20 UTC | 6h 5m |
| 2026-07-05 | UAL222D | CPT → EWR | Jul 5, 09:25 UTC | Jul 6, 00:20 UTC | 14h 55m |
| 2026-07-04 | UAL122D | - | Jul 4, 16:55 UTC | Jul 5, 06:25 UTC | 13h 30m |
| 2026-07-03 | UAL1855 | LAX → EWR | Jul 3, 23:20 UTC | Jul 4, 04:00 UTC | 4h 40m |
| 2026-07-03 | UAL3908 | - | Jul 3, 08:40 UTC | Jul 3, 21:10 UTC | 12h 30m |
| 2026-07-02 | UAL153 | HKG → LAX | Jul 2, 02:20 UTC | Jul 2, 02:25 UTC | 5m |
| 2026-07-01 | UAL152 | LAX → HKG | Jul 1, 13:00 UTC | Jul 1, 13:15 UTC | 15m |
| 2026-07-01 | UAL152 | LAX → HKG | Jul 1, 12:49 UTC | Jul 1, 15:01 UTC | 2h 12m |
| 2026-06-30 | UAL152 | LAX → HKG | Jun 30, 20:35 UTC | Jun 30, 21:35 UTC | 1h 0m |
| 2026-06-30 | UAL152 | LAX → HKG | Jun 30, 20:08 UTC | Jul 1, 10:20 UTC | 14h 12m |
| 2026-06-30 | UAL842 | - | Jun 30, 00:25 UTC | Jun 30, 13:10 UTC | 12h 46m |
| 2026-06-29 | UAL863 | SFO → SYD | Jun 29, 07:40 UTC | Jun 29, 21:54 UTC | 14h 15m |
| 2026-06-28 | UAL949 | LHR → SFO | Jun 28, 12:25 UTC | Jun 28, 22:27 UTC | 10h 2m |
| 2026-06-27 | UAL923 | - | Jun 27, 23:00 UTC | Jun 28, 08:44 UTC | 9h 45m |
| 2026-06-27 | UAL2692 | - | Jun 27, 13:40 UTC | Jun 27, 18:29 UTC | 4h 50m |
| 2026-06-26 | UAL1855 | - | Jun 26, 20:40 UTC | Jun 27, 01:00 UTC | 4h 20m |
| 2026-06-25 | UAL153 | HKG → LAX | Jun 25, 05:00 UTC | Jun 25, 18:10 UTC | 13h 10m |
| 2026-06-25 | UAL153 | HKG → LAX | Jun 25, 02:10 UTC | Jun 25, 02:25 UTC | 15m |
| 2026-06-24 | UAL152 | LAX → HKG | Jun 24, 13:00 UTC | Jun 24, 13:14 UTC | 15m |
| 2026-06-23 | UAL152 | LAX → HKG | Jun 23, 20:15 UTC | Jun 24, 10:30 UTC | 14h 15m |
| 2026-06-23 | UAL33 | - | Jun 23, 08:00 UTC | Jun 23, 17:39 UTC | 9h 40m |
| 2026-06-22 | UAL7 | - | Jun 22, 16:05 UTC | Jun 23, 04:39 UTC | 12h 35m |
| 2026-06-22 | UAL63 | - | Jun 22, 01:25 UTC | Jun 22, 02:00 UTC | 35m |
| 2026-06-22 | UAL63 | GRU → IAH | Jun 22, 01:16 UTC | Jun 22, 10:43 UTC | 9h 27m |
| 2026-06-21 | UAL62 | - | Jun 21, 00:19 UTC | Jun 21, 09:10 UTC | 8h 50m |
| 2026-06-20 | UAL6 | - | Jun 20, 08:09 UTC | Jun 20, 19:29 UTC | 11h 20m |
| 2026-06-19 | UAL32 | - | Jun 19, 18:20 UTC | Jun 20, 04:34 UTC | 10h 15m |
| 2026-06-18 | UAL935 | - | Jun 18, 13:05 UTC | Jun 18, 23:10 UTC | 10h 5m |
| 2026-06-18 | UAL935 | LHR → LAX | Jun 18, 13:05 UTC | Jun 18, 23:05 UTC | 10h 0m |
| 2026-06-18 | UAL923 | - | Jun 18, 00:50 UTC | Jun 18, 10:45 UTC | 9h 55m |
| 2026-06-17 | UAL2403 | - | Jun 17, 16:25 UTC | Jun 17, 21:20 UTC | 4h 55m |
| 2026-06-17 | UAL2303 | - | Jun 17, 06:30 UTC | Jun 17, 11:15 UTC | 4h 45m |
| 2026-06-17 | UAL2303 | LAX → EWR | Jun 17, 06:34 UTC | Jun 17, 11:10 UTC | 4h 36m |
| 2026-06-16 | UAL2403 | - | Jun 16, 16:15 UTC | Jun 16, 21:15 UTC | 5h 1m |
| 2026-06-15 | UAL187 | - | Jun 15, 20:00 UTC | Jun 16, 11:25 UTC | 15h 25m |
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 N29981 page for operator, model, and routing details .