sensors Mode-S transponder
A1A2A2
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N204UA · BOEING 777-200 · operated by UNITED AIRLINES INC
- Hex
- A1A2A2
- Octal
- 50321242
- Decimal
- 10,592,930
- Country
- US
- Tail
- N204UA
- Type
- B772
- Flights observed
- 229
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 19h ago
Last known position
Country allocation
The ICAO 24-bit address A1A2A2 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 |
|---|---|---|---|
| UAL18 | - | 12 | 2026-07-04 |
| UAL19 | - | 11 | 2026-07-03 |
| UAL888 | United Airlines | 10 | 2026-06-14 |
| UAL905 | - | 9 | 2026-06-26 |
| UAL2397 | United Airlines | 9 | 2026-05-12 |
| UAL14 | - | 9 | 2026-07-10 |
| UAL819 | United Airlines | 8 | 2026-05-14 |
| UAL46 | United Airlines | 7 | 2026-05-20 |
| UAL2238 | United Airlines | 7 | 2026-05-11 |
| UAL984 | - | 6 | 2026-06-22 |
| UAL939 | United Airlines | 6 | 2026-04-17 |
| UAL818 | United Airlines | 6 | 2026-05-15 |
| UAL47 | United Airlines | 6 | 2026-05-20 |
| UAL22 | United Airlines | 6 | 2026-06-27 |
| UAL194 | United Airlines | 6 | 2026-06-08 |
| UAL160 | United Airlines | 6 | 2026-06-09 |
| UAL889 | United Airlines | 5 | 2026-06-15 |
| UAL5 | United Airlines | 5 | 2026-05-06 |
| UAL23 | - | 5 | 2026-06-27 |
| UAL915 | - | 4 | 2026-07-09 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-14 | UAL195 | - | Jul 14, 10:25 UTC | Jul 14, 21:45 UTC | 11h 20m |
| 2026-07-13 | UAL102 | - | Jul 13, 22:25 UTC | Jul 14, 08:15 UTC | 9h 50m |
| 2026-07-11 | UAL879 | LHR → IAH | Jul 11, 09:25 UTC | Jul 11, 19:03 UTC | 9h 38m |
| 2026-07-11 | UAL879 | - | Jul 11, 09:25 UTC | Jul 11, 19:05 UTC | 9h 40m |
| 2026-07-10 | UAL14 | EWR → LHR | Jul 10, 23:35 UTC | Jul 11, 05:27 UTC | 5h 52m |
| 2026-07-10 | UAL14 | - | Jul 10, 23:25 UTC | Jul 11, 00:30 UTC | 1h 5m |
| 2026-07-10 | UAL56 | - | Jul 10, 08:30 UTC | Jul 10, 16:10 UTC | 7h 40m |
| 2026-07-09 | UAL915 | IAD → CDG | Jul 9, 23:05 UTC | Jul 10, 06:15 UTC | 7h 10m |
| 2026-07-09 | UAL804 | HND → IAD | Jul 9, 07:20 UTC | Jul 9, 20:15 UTC | 12h 55m |
| 2026-07-08 | UAL875 | SFO → HND | Jul 8, 18:40 UTC | Jul 9, 05:00 UTC | 10h 20m |
| 2026-07-07 | UAL673 | - | Jul 7, 14:40 UTC | Jul 7, 17:00 UTC | 2h 20m |
| 2026-07-07 | UAL673 | BCN → SFO | Jul 7, 14:36 UTC | Jul 8, 02:10 UTC | 11h 34m |
| 2026-07-07 | UAL673 | BCN → SFO | Jul 7, 14:36 UTC | Jul 8, 02:10 UTC | 11h 34m |
| 2026-07-07 | UAL672 | - | Jul 7, 01:25 UTC | Jul 7, 12:10 UTC | 10h 45m |
| 2026-07-06 | UAL195 | MUC → SFO | Jul 6, 10:05 UTC | Jul 6, 21:25 UTC | 11h 20m |
| 2026-07-05 | UAL102 | - | Jul 5, 22:00 UTC | Jul 6, 07:35 UTC | 9h 35m |
| 2026-07-05 | UAL879 | - | Jul 5, 09:40 UTC | Jul 5, 19:00 UTC | 9h 20m |
| 2026-07-04 | UAL14 | - | Jul 4, 23:35 UTC | Jul 5, 05:45 UTC | 6h 10m |
| 2026-07-04 | UAL18 | MXP → EWR | Jul 4, 08:06 UTC | Jul 4, 16:25 UTC | 8h 19m |
| 2026-07-04 | UAL18 | MXP → EWR | Jul 4, 08:05 UTC | Jul 4, 16:25 UTC | 8h 20m |
| 2026-07-03 | UAL19 | EWR → MXP | Jul 3, 22:03 UTC | Jul 4, 05:27 UTC | 7h 24m |
| 2026-07-03 | UAL19 | - | Jul 3, 22:20 UTC | Jul 3, 23:55 UTC | 1h 35m |
| 2026-07-02 | UAL3038 | - | Jul 2, 16:05 UTC | Jul 2, 17:55 UTC | 1h 50m |
| 2026-07-02 | UAL3038 | FRA → EWR | Jul 2, 15:50 UTC | Jul 3, 00:05 UTC | 8h 15m |
| 2026-07-02 | UAL3037 | - | Jul 2, 06:20 UTC | Jul 2, 13:05 UTC | 6h 45m |
| 2026-06-29 | UAL1333 | SFO → EWR | Jun 29, 21:14 UTC | Jun 30, 01:55 UTC | 4h 41m |
| 2026-06-29 | UAL1593 | - | Jun 29, 14:04 UTC | Jun 29, 19:24 UTC | 5h 20m |
| 2026-06-29 | UAL148 | - | Jun 29, 09:54 UTC | Jun 29, 10:00 UTC | 5m |
| 2026-06-29 | UAL148 | - | Jun 29, 00:29 UTC | Jun 29, 10:00 UTC | 9h 30m |
| 2026-06-29 | UAL148 | GRU → EWR | Jun 29, 00:21 UTC | Jun 29, 09:38 UTC | 9h 17m |
| 2026-06-28 | UAL149 | - | Jun 28, 04:10 UTC | Jun 28, 10:19 UTC | 6h 10m |
| 2026-06-28 | UAL149 | - | Jun 28, 01:10 UTC | Jun 28, 01:44 UTC | 35m |
| 2026-06-27 | UAL22 | DUB → EWR | Jun 27, 09:00 UTC | Jun 27, 15:45 UTC | 6h 45m |
| 2026-06-27 | UAL22 | DUB → EWR | Jun 27, 08:55 UTC | Jun 27, 15:49 UTC | 6h 54m |
| 2026-06-27 | UAL23 | EWR → DUB | Jun 27, 00:45 UTC | Jun 27, 06:29 UTC | 5h 44m |
| 2026-06-27 | UAL23 | EWR → DUB | Jun 27, 00:44 UTC | Jun 27, 06:19 UTC | 5h 35m |
| 2026-06-26 | UAL905 | - | Jun 26, 09:00 UTC | Jun 26, 16:05 UTC | 7h 5m |
| 2026-06-26 | UAL905 | LHR → EWR | Jun 26, 08:55 UTC | Jun 26, 16:07 UTC | 7h 12m |
| 2026-06-25 | UAL918 | IAD → LHR | Jun 25, 22:56 UTC | Jun 26, 05:45 UTC | 6h 49m |
| 2026-06-25 | UAL918 | - | Jun 25, 23:09 UTC | Jun 26, 00:30 UTC | 1h 20m |
| 2026-06-25 | UAL804 | - | Jun 25, 07:30 UTC | Jun 25, 08:09 UTC | 40m |
| 2026-06-25 | UAL804 | HND → IAD | Jun 25, 07:25 UTC | Jun 25, 19:40 UTC | 12h 15m |
| 2026-06-24 | UAL875 | SFO → HND | Jun 24, 18:25 UTC | Jun 25, 05:07 UTC | 10h 42m |
| 2026-06-24 | UAL875 | - | Jun 24, 18:44 UTC | Jun 25, 04:29 UTC | 9h 45m |
| 2026-06-23 | UAL673 | - | Jun 23, 14:39 UTC | Jun 24, 02:20 UTC | 11h 40m |
| 2026-06-23 | UAL672 | SFO → BCN | Jun 23, 01:29 UTC | Jun 23, 12:10 UTC | 10h 41m |
| 2026-06-23 | UAL672 | - | Jun 23, 01:20 UTC | Jun 23, 04:19 UTC | 3h 0m |
| 2026-06-22 | UAL984 | - | Jun 22, 08:29 UTC | Jun 22, 19:09 UTC | 10h 40m |
| 2026-06-22 | UAL57 | EWR → CDG | Jun 22, 00:55 UTC | Jun 22, 06:19 UTC | 5h 25m |
| 2026-06-21 | UAL57 | EWR → CDG | Jun 21, 23:40 UTC | Jun 22, 00:50 UTC | 1h 10m |
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 N204UA page for operator, model, and routing details .