sensors Mode-S transponder
A1F5FF
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N2250U · BOEING 777-300ER · operated by UNITED AIRLINES INC
- Hex
- A1F5FF
- Octal
- 50372777
- Decimal
- 10,614,271
- Country
- US
- Tail
- N2250U
- Type
- B77W
- Flights observed
- 241
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 37m ago
Last known position
Country allocation
The ICAO 24-bit address A1F5FF 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 |
|---|---|---|---|
| UAL1175 | - | 14 | 2026-07-07 |
| UAL950 | - | 12 | 2026-07-13 |
| UAL951 | - | 11 | 2026-07-14 |
| UAL201 | - | 11 | 2026-07-08 |
| UAL190 | - | 11 | 2026-07-07 |
| UAL989 | - | 10 | 2026-07-14 |
| UAL988 | - | 10 | 2026-07-13 |
| UAL877 | - | 10 | 2026-06-29 |
| UAL862 | - | 10 | 2026-06-30 |
| UAL43 | - | 10 | 2026-07-15 |
| UAL42 | - | 10 | 2026-07-13 |
| UAL189 | - | 10 | 2026-07-06 |
| UAL1844 | - | 9 | 2026-07-16 |
| UAL200 | - | 8 | 2026-07-09 |
| UAL872 | - | 7 | 2026-07-04 |
| UAL435 | - | 7 | 2026-07-12 |
| UAL878 | United Airlines | 6 | 2026-06-03 |
| UAL40 | - | 6 | 2026-07-15 |
| UAL871 | - | 5 | 2026-07-02 |
| UAL869 | United Airlines | 5 | 2026-06-02 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-18 | UAL78 | - | Jul 18, 08:45 UTC | Jul 18, 09:20 UTC | 35m |
| 2026-07-17 | UAL79 | EWR → NRT | Jul 17, 15:55 UTC | Jul 18, 04:55 UTC | 13h 1m |
| 2026-07-17 | UAL2416 | - | Jul 17, 07:25 UTC | Jul 17, 12:04 UTC | 4h 40m |
| 2026-07-16 | UAL1844 | - | Jul 16, 22:40 UTC | Jul 17, 03:55 UTC | 5h 15m |
| 2026-07-16 | UAL41 | - | Jul 16, 09:35 UTC | Jul 16, 18:15 UTC | 8h 40m |
| 2026-07-15 | UAL40 | - | Jul 15, 23:20 UTC | Jul 16, 00:10 UTC | 50m |
| 2026-07-15 | UAL40 | EWR → FCO | Jul 15, 22:53 UTC | Jul 16, 07:00 UTC | 8h 7m |
| 2026-07-15 | UAL43 | - | Jul 15, 10:10 UTC | Jul 15, 17:40 UTC | 7h 30m |
| 2026-07-15 | UAL43 | FRA → EWR | Jul 15, 10:14 UTC | Jul 15, 17:39 UTC | 7h 25m |
| 2026-07-14 | UAL989 | IAD → FRA | Jul 14, 22:15 UTC | Jul 15, 05:40 UTC | 7h 24m |
| 2026-07-14 | UAL951 | BRU → IAD | Jul 14, 10:35 UTC | Jul 14, 17:50 UTC | 7h 15m |
| 2026-07-13 | UAL950 | - | Jul 13, 22:30 UTC | Jul 14, 00:25 UTC | 1h 55m |
| 2026-07-13 | UAL950 | IAD → BRU | Jul 13, 22:03 UTC | Jul 14, 05:26 UTC | 7h 23m |
| 2026-07-13 | UAL988 | - | Jul 13, 11:10 UTC | Jul 13, 19:00 UTC | 7h 50m |
| 2026-07-13 | UAL42 | EWR → FRA | Jul 13, 01:30 UTC | Jul 13, 08:30 UTC | 7h 0m |
| 2026-07-12 | UAL435 | - | Jul 12, 15:50 UTC | Jul 12, 20:40 UTC | 4h 50m |
| 2026-07-11 | UAL1844 | - | Jul 11, 23:25 UTC | Jul 12, 04:30 UTC | 5h 5m |
| 2026-07-11 | UAL1844 | EWR → SFO | Jul 11, 22:34 UTC | Jul 12, 04:24 UTC | 5h 50m |
| 2026-07-11 | UAL41 | - | Jul 11, 09:40 UTC | Jul 11, 11:40 UTC | 2h 0m |
| 2026-07-11 | UAL41 | FCO → EWR | Jul 11, 09:27 UTC | Jul 11, 18:08 UTC | 8h 41m |
| 2026-07-10 | UAL40 | EWR → FCO | Jul 10, 22:08 UTC | Jul 11, 05:54 UTC | 7h 46m |
| 2026-07-10 | UAL40 | - | Jul 10, 22:20 UTC | Jul 10, 23:50 UTC | 1h 30m |
| 2026-07-10 | UAL43 | - | Jul 10, 10:05 UTC | Jul 10, 18:15 UTC | 8h 10m |
| 2026-07-10 | UAL42 | - | Jul 10, 00:30 UTC | Jul 10, 01:55 UTC | 1h 25m |
| 2026-07-10 | UAL42 | EWR → FRA | Jul 10, 00:15 UTC | Jul 10, 07:28 UTC | 7h 13m |
| 2026-07-09 | UAL435 | - | Jul 9, 16:35 UTC | Jul 9, 21:30 UTC | 4h 55m |
| 2026-07-09 | UAL1346 | - | Jul 9, 08:55 UTC | Jul 9, 09:10 UTC | 15m |
| 2026-07-09 | UAL1346 | HNL → SFO | Jul 9, 08:39 UTC | Jul 9, 13:20 UTC | 4h 41m |
| 2026-07-09 | UAL200 | - | Jul 9, 03:55 UTC | Jul 9, 04:20 UTC | 25m |
| 2026-07-08 | UAL201 | - | Jul 8, 00:50 UTC | Jul 8, 01:00 UTC | 10m |
| 2026-07-08 | UAL201 | HNL → GUM | Jul 8, 00:44 UTC | Jul 8, 08:14 UTC | 7h 30m |
| 2026-07-07 | UAL1175 | - | Jul 7, 21:05 UTC | Jul 7, 21:30 UTC | 25m |
| 2026-07-07 | UAL1175 | - | Jul 7, 17:00 UTC | Jul 7, 17:30 UTC | 30m |
| 2026-07-07 | UAL1175 | SFO → HNL | Jul 7, 16:43 UTC | Jul 7, 21:28 UTC | 4h 45m |
| 2026-07-07 | UAL190 | - | Jul 7, 01:25 UTC | Jul 7, 01:55 UTC | 30m |
| 2026-07-07 | UAL190 | MNL → SFO | Jul 7, 01:01 UTC | Jul 7, 13:30 UTC | 12h 29m |
| 2026-07-07 | UAL190 | MNL → SFO | Jul 7, 01:01 UTC | Jul 7, 13:28 UTC | 12h 27m |
| 2026-07-06 | UAL189 | - | Jul 6, 08:30 UTC | Jul 6, 08:55 UTC | 25m |
| 2026-07-06 | UAL189 | SFO → MNL | Jul 6, 08:24 UTC | Jul 6, 21:35 UTC | 13h 11m |
| 2026-07-05 | UAL810 | - | Jul 5, 13:45 UTC | Jul 6, 01:45 UTC | 12h 0m |
| 2026-07-04 | UAL809 | SFO → MNL | Jul 4, 21:40 UTC | Jul 5, 10:30 UTC | 12h 50m |
| 2026-07-04 | UAL872 | TPE → SFO | Jul 4, 02:33 UTC | Jul 4, 13:33 UTC | 11h 0m |
| 2026-07-04 | UAL872 | TPE → SFO | Jul 4, 02:25 UTC | Jul 4, 13:30 UTC | 11h 5m |
| 2026-07-02 | UAL871 | - | Jul 2, 22:35 UTC | Jul 3, 10:45 UTC | 12h 10m |
| 2026-07-02 | UAL858 | - | Jul 2, 05:15 UTC | Jul 2, 14:50 UTC | 9h 35m |
| 2026-07-01 | UAL858 | - | Jul 1, 07:50 UTC | Jul 2, 06:51 UTC | 23h 1m |
| 2026-07-01 | UAL857 | - | Jul 1, 06:20 UTC | Jul 2, 05:45 UTC | 23h 25m |
| 2026-06-30 | UAL857 | - | Jun 30, 20:50 UTC | Jul 1, 08:15 UTC | 11h 25m |
| 2026-06-30 | UAL862 | - | Jun 30, 04:10 UTC | Jun 30, 15:45 UTC | 11h 35m |
| 2026-06-30 | UAL862 | HKG → SFO | Jun 30, 04:11 UTC | Jun 30, 16:19 UTC | 12h 8m |
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 N2250U page for operator, model, and routing details .