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
- 89
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 1h 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 |
|---|---|---|---|
| UAL153 | United Airlines | 9 | 2026-05-20 |
| UAL152 | United Airlines | 8 | 2026-05-19 |
| UAL199 | United Airlines | 6 | 2026-05-21 |
| UAL198 | United Airlines | 6 | 2026-05-21 |
| UAL2222 | United Airlines | 4 | 2026-05-23 |
| UAL1122 | United Airlines | 4 | 2026-05-23 |
| UAL863 | United Airlines | 3 | 2026-04-24 |
| UAL842 | United Airlines | 3 | 2026-04-21 |
| UAL821 | United Airlines | 3 | 2026-04-13 |
| UAL187 | United Airlines | 3 | 2026-05-25 |
| UAL1855 | United Airlines | 3 | 2026-04-17 |
| UAL1227 | United Airlines | 3 | 2026-04-23 |
| UAL923 | United Airlines | 2 | 2026-05-28 |
| UAL870 | United Airlines | 2 | 2026-04-25 |
| UAL839 | - | 2 | 2026-04-14 |
| UAL820 | United Airlines | 2 | 2026-04-13 |
| UAL713 | United Airlines | 2 | 2026-05-07 |
| UAL61 | United Airlines | 2 | 2026-05-06 |
| UAL60 | United Airlines | 2 | 2026-05-05 |
| UAL33 | United Airlines | 2 | 2026-05-16 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-05-29 | UAL935 | LHR → LAX | May 29, 12:35 UTC | May 29, 22:45 UTC | 10h 11m |
| 2026-05-28 | UAL923 | LAX → LHR | May 28, 22:55 UTC | May 29, 09:00 UTC | 10h 5m |
| 2026-05-26 | UAL2403 | RDU → EWR | May 26, 16:59 UTC | May 26, 21:55 UTC | 4h 55m |
| 2026-05-25 | UAL187 | JNB → EWR | May 25, 20:15 UTC | May 25, 20:34 UTC | 20m |
| 2026-05-25 | UAL187 | JNB → EWR | May 25, 20:19 UTC | May 26, 11:27 UTC | 15h 8m |
| 2026-05-25 | UAL187 | JNB → EWR | May 25, 20:19 UTC | May 26, 11:42 UTC | 15h 23m |
| 2026-05-25 | UAL188 | EWR → JNB | May 25, 01:55 UTC | May 25, 16:00 UTC | 14h 5m |
| 2026-05-23 | UAL2222 | IAD → CPT | May 23, 18:10 UTC | May 24, 08:55 UTC | 14h 45m |
| 2026-05-23 | UAL1122 | EWR → CPT | May 23, 01:16 UTC | May 23, 15:20 UTC | 14h 4m |
| 2026-05-23 | UAL1122 | EWR → CPT | May 23, 01:30 UTC | May 23, 15:20 UTC | 13h 50m |
| 2026-05-22 | UAL2303 | IAD → SAN | May 22, 06:45 UTC | May 22, 11:20 UTC | 4h 34m |
| 2026-05-21 | UAL199 | PVG → LAX | May 21, 13:30 UTC | May 21, 14:50 UTC | 1h 20m |
| 2026-05-21 | UAL199 | PVG → LAX | May 21, 06:25 UTC | May 21, 23:40 UTC | 17h 15m |
| 2026-05-21 | UAL199 | PVG → LAX | May 21, 00:50 UTC | May 21, 23:40 UTC | 22h 50m |
| 2026-05-21 | UAL198 | LAX → PVG | May 21, 00:30 UTC | May 21, 22:45 UTC | 22h 15m |
| 2026-05-20 | UAL198 | LAX → PVG | May 20, 20:50 UTC | May 21, 14:50 UTC | 18h 0m |
| 2026-05-20 | UAL198 | LAX → PVG | May 20, 20:10 UTC | May 21, 08:10 UTC | 12h 0m |
| 2026-05-20 | UAL198 | LAX → PVG | May 20, 20:08 UTC | May 21, 09:24 UTC | 13h 16m |
| 2026-05-20 | UAL153 | HKG → LAX | May 20, 05:18 UTC | May 20, 17:23 UTC | 12h 5m |
| 2026-05-20 | UAL153 | HKG → LAX | May 20, 05:05 UTC | May 20, 17:35 UTC | 12h 30m |
| 2026-05-20 | UAL153 | HKG → LAX | May 20, 02:30 UTC | May 20, 02:45 UTC | 15m |
| 2026-05-19 | UAL152 | LAX → HKG | May 19, 13:10 UTC | May 19, 13:20 UTC | 10m |
| 2026-05-18 | UAL152 | LAX → HKG | May 18, 19:10 UTC | May 19, 08:45 UTC | 13h 35m |
| 2026-05-18 | UAL152 | LAX → HKG | May 18, 19:17 UTC | May 19, 09:56 UTC | 14h 39m |
| 2026-05-17 | UAL199 | PVG → LAX | May 17, 13:35 UTC | May 17, 15:15 UTC | 1h 40m |
| 2026-05-17 | UAL199 | PVG → LAX | May 17, 12:36 UTC | May 17, 23:40 UTC | 11h 4m |
| 2026-05-17 | UAL199 | PVG → LAX | May 17, 06:25 UTC | May 17, 23:50 UTC | 17h 25m |
| 2026-05-16 | UAL198 | LAX → PVG | May 16, 20:10 UTC | May 17, 07:50 UTC | 11h 40m |
| 2026-05-16 | UAL198 | LAX → PVG | May 16, 20:08 UTC | May 17, 08:55 UTC | 12h 47m |
| 2026-05-16 | UAL33 | NRT → LAX | May 16, 08:01 UTC | May 16, 17:10 UTC | 9h 10m |
| 2026-05-16 | UAL33 | NRT → LAX | May 16, 08:05 UTC | May 16, 17:02 UTC | 8h 57m |
| 2026-05-15 | UAL143 | DEN → NRT | May 15, 17:55 UTC | May 16, 05:10 UTC | 11h 15m |
| 2026-05-14 | UAL26 | LHR → DEN | May 14, 11:50 UTC | May 14, 20:50 UTC | 9h 0m |
| 2026-05-14 | UAL26 | LHR → DEN | May 14, 11:25 UTC | May 14, 20:45 UTC | 9h 20m |
| 2026-05-12 | UAL923 | LAX → LHR | May 12, 22:45 UTC | May 13, 08:50 UTC | 10h 5m |
| 2026-05-12 | UAL2692 | IAD → PHL | May 12, 14:00 UTC | May 12, 19:05 UTC | 5h 5m |
| 2026-05-12 | UAL2222 | IAD → CPT | May 12, 09:45 UTC | May 12, 09:50 UTC | 5m |
| 2026-05-11 | UAL2222 | IAD → CPT | May 11, 18:20 UTC | May 11, 18:40 UTC | 20m |
| 2026-05-11 | UAL2222 | IAD → CPT | May 11, 18:22 UTC | May 12, 09:30 UTC | 15h 8m |
| 2026-05-11 | UAL1122 | EWR → CPT | May 11, 15:05 UTC | May 11, 15:25 UTC | 20m |
| 2026-05-11 | UAL1122 | EWR → CPT | May 11, 02:00 UTC | May 11, 08:25 UTC | 6h 25m |
| 2026-05-10 | UAL78 | NRT → EWR | May 10, 08:40 UTC | May 10, 20:35 UTC | 11h 55m |
| 2026-05-09 | UAL32 | LAX → NRT | May 9, 17:55 UTC | May 10, 04:56 UTC | 11h 1m |
| 2026-05-09 | UAL32 | LAX → NRT | May 9, 18:00 UTC | May 10, 05:10 UTC | 11h 10m |
| 2026-05-08 | UAL2692 | IAD → PHL | May 8, 13:45 UTC | May 8, 18:45 UTC | 5h 0m |
| 2026-05-07 | UAL713 | ORD → DEL | May 7, 18:40 UTC | May 7, 23:14 UTC | 4h 35m |
| 2026-05-07 | UAL713 | ORD → DEL | May 7, 18:30 UTC | May 7, 23:10 UTC | 4h 40m |
| 2026-05-06 | UAL61 | BRU → EWR | May 6, 01:09 UTC | May 6, 14:45 UTC | 13h 36m |
| 2026-05-06 | UAL61 | BRU → EWR | May 6, 01:05 UTC | May 6, 02:20 UTC | 1h 15m |
| 2026-05-05 | UAL60 | SFO → MEL | May 5, 07:15 UTC | May 5, 22:24 UTC | 15h 9m |
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 .