sensors Mode-S transponder
AA73B9
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N77261 · BOEING 737-800 · operated by UNITED AIRLINES INC
- Hex
- AA73B9
- Octal
- 52471671
- Decimal
- 11,170,745
- Country
- US
- Tail
- N77261
- Type
- B738
- Flights observed
- 82
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 14d ago
Last known position
Country allocation
The ICAO 24-bit address AA73B9 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 |
|---|---|---|---|
| UAL848 | United Airlines | 10 | 2026-05-11 |
| UAL33 | United Airlines | 10 | 2026-05-13 |
| UAL849 | United Airlines | 9 | 2026-05-11 |
| UAL197 | United Airlines | 7 | 2026-05-14 |
| UAL827 | United Airlines | 6 | 2026-05-11 |
| UAL142 | United Airlines | 6 | 2026-05-14 |
| UAL873 | United Airlines | 5 | 2026-05-10 |
| UAL196 | United Airlines | 5 | 2026-05-07 |
| UAL837 | United Airlines | 4 | 2026-05-08 |
| UAL143 | United Airlines | 4 | 2026-05-13 |
| UAL32 | United Airlines | 3 | 2026-05-07 |
| UAL865 | United Airlines | 2 | 2026-04-27 |
| UAL838 | United Airlines | 2 | 2026-05-09 |
| UAL3895 | United Airlines | 2 | 2026-05-15 |
| UAL864 | United Airlines | 1 | 2026-05-12 |
| UAL3897 | United Airlines | 1 | 2026-05-16 |
| UAL3896 | United Airlines | 1 | 2026-05-15 |
| UAL184 | United Airlines | 1 | 2026-05-03 |
| UAL183 | United Airlines | 1 | 2026-05-03 |
| UAL157 | United Airlines | 1 | 2026-04-27 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-05-16 | UAL3897 | PBI → EWR | May 16, 00:45 UTC | May 16, 05:40 UTC | 4h 55m |
| 2026-05-15 | UAL3896 | IAH → EWR | May 15, 18:25 UTC | May 15, 23:05 UTC | 4h 40m |
| 2026-05-15 | UAL3895 | ORD → TPA | May 15, 02:08 UTC | May 15, 06:41 UTC | 4h 33m |
| 2026-05-14 | UAL3895 | ORD → TPA | May 14, 08:20 UTC | May 15, 06:45 UTC | 22h 25m |
| 2026-05-14 | UAL197 | NRT → GUM | May 14, 08:05 UTC | May 15, 06:15 UTC | 22h 10m |
| 2026-05-14 | UAL142 | NRT → DEN | May 14, 01:50 UTC | May 14, 06:15 UTC | 4h 25m |
| 2026-05-14 | UAL142 | NRT → DEN | May 14, 01:58 UTC | May 14, 06:01 UTC | 4h 3m |
| 2026-05-13 | UAL143 | DEN → NRT | May 13, 08:00 UTC | May 13, 12:15 UTC | 4h 15m |
| 2026-05-13 | UAL33 | NRT → LAX | May 13, 04:55 UTC | May 13, 05:55 UTC | 1h 0m |
| 2026-05-12 | UAL33 | NRT → LAX | May 12, 09:25 UTC | May 13, 05:55 UTC | 20h 30m |
| 2026-05-12 | UAL864 | GUM → NRT | May 12, 05:40 UTC | May 12, 06:30 UTC | 50m |
| 2026-05-11 | UAL848 | HND → GUM | May 11, 15:00 UTC | May 11, 17:59 UTC | 2h 59m |
| 2026-05-11 | UAL848 | HND → GUM | May 11, 14:50 UTC | May 11, 15:30 UTC | 40m |
| 2026-05-11 | UAL849 | GUM → HND | May 11, 12:30 UTC | May 11, 13:20 UTC | 50m |
| 2026-05-11 | UAL849 | GUM → HND | May 11, 09:44 UTC | May 11, 13:11 UTC | 3h 27m |
| 2026-05-11 | UAL827 | NRT → GUM | May 11, 02:15 UTC | May 11, 02:50 UTC | 35m |
| 2026-05-10 | UAL873 | GUM → NRT | May 10, 09:50 UTC | May 10, 10:35 UTC | 45m |
| 2026-05-09 | UAL197 | NRT → GUM | May 9, 09:00 UTC | May 9, 09:35 UTC | 35m |
| 2026-05-09 | UAL197 | NRT → GUM | May 9, 08:47 UTC | May 9, 12:17 UTC | 3h 30m |
| 2026-05-09 | UAL838 | NRT → SFO | May 9, 02:05 UTC | May 9, 05:00 UTC | 2h 55m |
| 2026-05-08 | UAL837 | SFO → NRT | May 8, 09:19 UTC | May 8, 13:00 UTC | 3h 40m |
| 2026-05-08 | UAL33 | NRT → LAX | May 8, 05:00 UTC | May 8, 05:44 UTC | 45m |
| 2026-05-07 | UAL32 | LAX → NRT | May 7, 09:10 UTC | May 7, 09:55 UTC | 45m |
| 2026-05-07 | UAL32 | LAX → NRT | May 7, 09:22 UTC | May 7, 13:35 UTC | 4h 13m |
| 2026-05-07 | UAL196 | GUM → NRT | May 7, 04:55 UTC | May 7, 05:45 UTC | 50m |
| 2026-05-06 | UAL827 | NRT → GUM | May 6, 02:15 UTC | May 6, 02:50 UTC | 35m |
| 2026-05-05 | UAL873 | GUM → NRT | May 5, 07:08 UTC | May 5, 10:28 UTC | 3h 20m |
| 2026-05-04 | UAL848 | HND → GUM | May 4, 14:50 UTC | May 4, 15:25 UTC | 35m |
| 2026-05-04 | UAL849 | GUM → HND | May 4, 02:30 UTC | May 4, 12:55 UTC | 10h 25m |
| 2026-05-03 | UAL184 | MNL → GUM | May 3, 14:55 UTC | May 3, 15:20 UTC | 25m |
| 2026-05-03 | UAL183 | GUM → MNL | May 3, 09:29 UTC | May 3, 12:45 UTC | 3h 16m |
| 2026-05-03 | UAL827 | NRT → GUM | May 3, 02:25 UTC | May 3, 12:15 UTC | 9h 49m |
| 2026-05-01 | UAL848 | HND → GUM | May 1, 14:50 UTC | May 2, 10:10 UTC | 19h 21m |
| 2026-05-01 | UAL849 | GUM → HND | May 1, 09:44 UTC | May 1, 13:04 UTC | 3h 20m |
| 2026-05-01 | UAL849 | GUM → HND | May 1, 02:40 UTC | May 1, 13:10 UTC | 10h 30m |
| 2026-04-30 | UAL137 | GUM → NGO | Apr 30, 21:33 UTC | May 1, 00:54 UTC | 3h 21m |
| 2026-04-30 | UAL197 | NRT → GUM | Apr 30, 08:20 UTC | Apr 30, 08:55 UTC | 35m |
| 2026-04-30 | UAL197 | NRT → GUM | Apr 30, 08:27 UTC | Apr 30, 11:31 UTC | 3h 4m |
| 2026-04-30 | UAL142 | NRT → DEN | Apr 30, 02:00 UTC | Apr 30, 05:55 UTC | 3h 55m |
| 2026-04-30 | UAL142 | NRT → DEN | Apr 30, 01:58 UTC | Apr 30, 05:47 UTC | 3h 49m |
| 2026-04-29 | UAL143 | DEN → NRT | Apr 29, 08:05 UTC | Apr 29, 12:15 UTC | 4h 11m |
| 2026-04-29 | UAL33 | NRT → LAX | Apr 29, 04:55 UTC | Apr 29, 05:40 UTC | 45m |
| 2026-04-28 | UAL33 | NRT → LAX | Apr 28, 09:05 UTC | Apr 29, 05:40 UTC | 20h 35m |
| 2026-04-28 | UAL196 | GUM → NRT | Apr 28, 02:24 UTC | Apr 28, 05:38 UTC | 3h 14m |
| 2026-04-27 | UAL196 | GUM → NRT | Apr 27, 17:00 UTC | Apr 28, 05:45 UTC | 12h 45m |
| 2026-04-27 | UAL157 | GUM → ROR | Apr 27, 15:05 UTC | Apr 27, 15:20 UTC | 15m |
| 2026-04-27 | UAL865 | NRT → GUM | Apr 27, 07:45 UTC | Apr 27, 08:15 UTC | 30m |
| 2026-04-27 | UAL865 | NRT → GUM | Apr 27, 07:47 UTC | Apr 27, 11:11 UTC | 3h 24m |
| 2026-04-27 | UAL838 | NRT → SFO | Apr 27, 02:00 UTC | Apr 27, 05:00 UTC | 3h 0m |
| 2026-04-26 | UAL837 | SFO → NRT | Apr 26, 12:25 UTC | Apr 26, 12:50 UTC | 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 N77261 page for operator, model, and routing details .