sensors Mode-S transponder
A2B501
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N2737U · BOEING 777-300ER · operated by UNITED AIRLINES INC
- Hex
- A2B501
- Octal
- 50532401
- Decimal
- 10,663,169
- Country
- US
- Tail
- N2737U
- Type
- B77W
- Flights observed
- 238
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 10h ago
Last known position
Country allocation
The ICAO 24-bit address A2B501 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 |
|---|---|---|---|
| UAL189 | - | 20 | 2026-07-05 |
| UAL190 | - | 17 | 2026-07-06 |
| UAL1175 | - | 13 | 2026-07-13 |
| UAL809 | - | 12 | 2026-07-03 |
| UAL989 | - | 10 | 2026-06-25 |
| UAL951 | United Airlines | 10 | 2026-06-25 |
| UAL810 | - | 10 | 2026-07-04 |
| UAL201 | - | 9 | 2026-07-14 |
| UAL988 | - | 8 | 2026-06-24 |
| UAL872 | - | 8 | 2026-07-13 |
| UAL43 | - | 8 | 2026-06-29 |
| UAL42 | - | 8 | 2026-06-29 |
| UAL871 | - | 6 | 2026-07-12 |
| UAL869 | United Airlines | 6 | 2026-06-03 |
| UAL435 | - | 6 | 2026-06-23 |
| UAL200 | - | 6 | 2026-06-23 |
| UAL1844 | - | 6 | 2026-06-26 |
| UAL950 | - | 5 | 2026-06-24 |
| UAL878 | United Airlines | 5 | 2026-06-04 |
| UAL858 | United Airlines | 5 | 2026-05-16 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-14 | UAL201 | - | Jul 14, 00:45 UTC | Jul 14, 01:10 UTC | 25m |
| 2026-07-13 | UAL1175 | - | Jul 13, 21:05 UTC | Jul 13, 21:25 UTC | 20m |
| 2026-07-13 | UAL1175 | - | Jul 13, 16:45 UTC | Jul 13, 17:15 UTC | 30m |
| 2026-07-13 | UAL872 | - | Jul 13, 02:01 UTC | Jul 13, 13:35 UTC | 11h 35m |
| 2026-07-12 | UAL871 | - | Jul 12, 09:50 UTC | Jul 12, 10:15 UTC | 25m |
| 2026-07-11 | UAL871 | - | Jul 11, 22:10 UTC | Jul 12, 08:45 UTC | 10h 35m |
| 2026-07-11 | UAL838 | - | Jul 11, 08:20 UTC | Jul 11, 08:50 UTC | 30m |
| 2026-07-11 | UAL838 | NRT → SFO | Jul 11, 08:31 UTC | Jul 11, 17:37 UTC | 9h 6m |
| 2026-07-10 | UAL79 | EWR → NRT | Jul 10, 16:02 UTC | Jul 11, 04:39 UTC | 12h 37m |
| 2026-07-10 | UAL79 | - | Jul 10, 16:00 UTC | Jul 11, 04:40 UTC | 12h 40m |
| 2026-07-10 | UAL2416 | - | Jul 10, 07:45 UTC | Jul 10, 12:20 UTC | 4h 35m |
| 2026-07-10 | UAL3935 | - | Jul 10, 00:20 UTC | Jul 10, 04:45 UTC | 4h 25m |
| 2026-07-08 | UAL200C | - | Jul 8, 21:40 UTC | Jul 8, 21:55 UTC | 15m |
| 2026-07-07 | UAL201D | - | Jul 7, 18:25 UTC | Jul 7, 18:45 UTC | 20m |
| 2026-07-07 | UAL201D | HNL → GUM | Jul 7, 18:19 UTC | Jul 8, 01:35 UTC | 7h 16m |
| 2026-07-06 | UAL1175 | - | Jul 6, 21:00 UTC | Jul 6, 21:15 UTC | 15m |
| 2026-07-06 | UAL1175 | - | Jul 6, 16:40 UTC | Jul 6, 17:10 UTC | 30m |
| 2026-07-06 | UAL190 | - | Jul 6, 00:55 UTC | Jul 6, 12:50 UTC | 11h 55m |
| 2026-07-05 | UAL189 | - | Jul 5, 21:50 UTC | Jul 5, 22:05 UTC | 15m |
| 2026-07-05 | UAL189 | SFO → MNL | Jul 5, 08:19 UTC | Jul 5, 21:31 UTC | 13h 12m |
| 2026-07-05 | UAL189 | - | Jul 5, 08:40 UTC | Jul 5, 09:10 UTC | 30m |
| 2026-07-04 | UAL810 | - | Jul 4, 13:55 UTC | Jul 4, 14:15 UTC | 20m |
| 2026-07-04 | UAL810 | MNL → SFO | Jul 4, 13:41 UTC | Jul 5, 01:58 UTC | 12h 17m |
| 2026-07-03 | UAL809 | SFO → MNL | Jul 3, 21:43 UTC | Jul 4, 10:32 UTC | 12h 49m |
| 2026-07-03 | UAL809 | - | Jul 3, 21:45 UTC | Jul 4, 10:15 UTC | 12h 30m |
| 2026-07-02 | UAL810 | - | Jul 2, 16:35 UTC | Jul 3, 04:10 UTC | 11h 35m |
| 2026-07-01 | UAL809 | SFO → MNL | Jul 1, 22:28 UTC | Jul 2, 12:02 UTC | 13h 34m |
| 2026-07-01 | UAL809 | SFO → MNL | Jul 1, 23:10 UTC | Jul 2, 12:00 UTC | 12h 50m |
| 2026-06-30 | UAL1960 | EWR → SFO | Jun 30, 01:20 UTC | Jun 30, 06:16 UTC | 4h 56m |
| 2026-06-30 | UAL1960 | EWR → SFO | Jun 30, 01:14 UTC | Jun 30, 06:20 UTC | 5h 5m |
| 2026-06-29 | UAL43 | - | Jun 29, 10:50 UTC | Jun 29, 18:14 UTC | 7h 25m |
| 2026-06-29 | UAL43 | FRA → EWR | Jun 29, 10:31 UTC | Jun 29, 18:35 UTC | 8h 4m |
| 2026-06-29 | UAL42 | EWR → FRA | Jun 29, 00:45 UTC | Jun 29, 07:39 UTC | 6h 54m |
| 2026-06-29 | UAL42 | - | Jun 29, 00:54 UTC | Jun 29, 06:14 UTC | 5h 20m |
| 2026-06-28 | UAL78 | NRT → EWR | Jun 28, 08:50 UTC | Jun 28, 20:45 UTC | 11h 55m |
| 2026-06-27 | UAL79 | EWR → NRT | Jun 27, 16:30 UTC | Jun 28, 06:05 UTC | 13h 35m |
| 2026-06-27 | UAL2416 | SFO → EWR | Jun 27, 07:55 UTC | Jun 27, 12:19 UTC | 4h 25m |
| 2026-06-26 | UAL1844 | - | Jun 26, 22:40 UTC | Jun 27, 04:15 UTC | 5h 35m |
| 2026-06-26 | UAL43 | - | Jun 26, 09:59 UTC | Jun 26, 17:44 UTC | 7h 45m |
| 2026-06-25 | UAL989 | IAD → FRA | Jun 25, 21:44 UTC | Jun 26, 04:55 UTC | 7h 10m |
| 2026-06-25 | UAL951 | BRU → IAD | Jun 25, 10:35 UTC | Jun 25, 12:04 UTC | 1h 30m |
| 2026-06-25 | UAL951 | BRU → IAD | Jun 25, 10:24 UTC | Jun 25, 18:33 UTC | 8h 9m |
| 2026-06-24 | UAL950 | IAD → BRU | Jun 24, 22:08 UTC | Jun 25, 04:57 UTC | 6h 49m |
| 2026-06-24 | UAL950 | - | Jun 24, 22:14 UTC | Jun 25, 04:14 UTC | 6h 0m |
| 2026-06-24 | UAL988 | - | Jun 24, 10:45 UTC | Jun 24, 19:10 UTC | 8h 25m |
| 2026-06-24 | UAL42 | EWR → FRA | Jun 24, 00:10 UTC | Jun 24, 07:01 UTC | 6h 51m |
| 2026-06-24 | UAL42 | - | Jun 24, 00:34 UTC | Jun 24, 06:15 UTC | 5h 40m |
| 2026-06-23 | UAL435 | SFO → EWR | Jun 23, 15:44 UTC | Jun 23, 20:29 UTC | 4h 45m |
| 2026-06-23 | UAL1346 | - | Jun 23, 08:35 UTC | Jun 23, 12:55 UTC | 4h 20m |
| 2026-06-23 | UAL200 | - | Jun 23, 03:49 UTC | Jun 23, 04:14 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 N2737U page for operator, model, and routing details .