sensors Mode-S transponder
A254DD
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N24979 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A254DD
- Octal
- 50452335
- Decimal
- 10,638,557
- Country
- US
- Tail
- N24979
- Type
- B789
- Flights observed
- 207
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- Jul 26, 21:15 UTC
Current position
Country allocation
The ICAO 24-bit address A254DD 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 |
|---|---|---|---|
| UAL152 | United Airlines | 12 | 2026-07-07 |
| UAL199 | - | 11 | 2026-07-19 |
| UAL153 | United Airlines | 10 | 2026-07-08 |
| UAL198 | United Airlines | 9 | 2026-07-18 |
| UAL29 | United Airlines | 8 | 2026-05-16 |
| UAL177 | United Airlines | 8 | 2026-07-25 |
| UAL28 | United Airlines | 7 | 2026-05-17 |
| UAL115 | United Airlines | 7 | 2026-05-08 |
| UAL892 | - | 6 | 2026-06-29 |
| UAL2 | United Airlines | 6 | 2026-04-16 |
| UAL178 | United Airlines | 6 | 2026-07-25 |
| UAL114 | United Airlines | 6 | 2026-05-09 |
| UAL893 | - | 5 | 2026-06-28 |
| UAL142 | United Airlines | 5 | 2026-07-22 |
| UAL863 | - | 4 | 2026-07-01 |
| UAL761 | United Airlines | 4 | 2026-06-14 |
| UAL60 | - | 4 | 2026-06-27 |
| UAL6 | - | 4 | 2026-06-22 |
| UAL32 | United Airlines | 4 | 2026-07-21 |
| UAL27 | United Airlines | 4 | 2026-07-24 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-26 | UAL263 | EWR → PBI | Jul 26, 14:10 UTC | Jul 26, 21:15 UTC | 7h 5m |
| 2026-07-26 | UAL262 | DEN → LHR | Jul 26, 02:45 UTC | Jul 26, 11:07 UTC | 8h 22m |
| 2026-07-26 | UAL262 | DEN → LHR | Jul 26, 02:50 UTC | Jul 26, 05:15 UTC | 2h 25m |
| 2026-07-25 | UAL178 | KIX → GUM | Jul 25, 12:40 UTC | Jul 25, 23:30 UTC | 10h 50m |
| 2026-07-25 | UAL177 | GUM → KIX | Jul 25, 00:10 UTC | Jul 25, 10:00 UTC | 9h 50m |
| 2026-07-24 | UAL26 | LHR → DEN | Jul 24, 11:00 UTC | Jul 24, 20:05 UTC | 9h 5m |
| 2026-07-24 | UAL27 | DEN → LHR | Jul 24, 00:00 UTC | Jul 24, 07:15 UTC | 7h 15m |
| 2026-07-23 | UAL27 | DEN → LHR | Jul 23, 23:58 UTC | Jul 24, 08:09 UTC | 8h 11m |
| 2026-07-23 | UAL181 | FRA → DEN | Jul 23, 09:56 UTC | Jul 23, 19:35 UTC | 9h 39m |
| 2026-07-23 | UAL181 | FRA → DEN | Jul 23, 09:50 UTC | Jul 23, 11:50 UTC | 2h 0m |
| 2026-07-22 | UAL182 | DEN → FRA | Jul 22, 22:50 UTC | Jul 23, 07:35 UTC | 8h 45m |
| 2026-07-22 | UAL142 | NRT → DEN | Jul 22, 16:05 UTC | Jul 22, 18:40 UTC | 2h 35m |
| 2026-07-21 | UAL32 | LAX → NRT | Jul 21, 18:35 UTC | Jul 21, 19:35 UTC | 1h 0m |
| 2026-07-21 | UAL32 | LAX → NRT | Jul 21, 18:15 UTC | Jul 22, 05:04 UTC | 10h 49m |
| 2026-07-19 | UAL199 | - | Jul 19, 13:20 UTC | Jul 19, 14:55 UTC | 1h 35m |
| 2026-07-19 | UAL199 | - | Jul 19, 06:20 UTC | Jul 20, 00:15 UTC | 17h 55m |
| 2026-07-18 | UAL198 | LAX → PVG | Jul 18, 21:00 UTC | Jul 19, 08:15 UTC | 11h 15m |
| 2026-07-18 | UAL198 | LAX → PVG | Jul 18, 21:01 UTC | Jul 19, 09:04 UTC | 12h 3m |
| 2026-07-17 | UAL935 | - | Jul 17, 12:30 UTC | Jul 17, 22:49 UTC | 10h 20m |
| 2026-07-17 | UAL948 | SFO → LHR | Jul 17, 00:50 UTC | Jul 17, 10:15 UTC | 9h 25m |
| 2026-07-16 | UAL870 | - | Jul 16, 01:15 UTC | Jul 16, 14:45 UTC | 13h 30m |
| 2026-07-15 | UAL839 | - | Jul 15, 07:05 UTC | Jul 15, 21:05 UTC | 14h 0m |
| 2026-07-14 | UAL199 | - | Jul 14, 13:10 UTC | Jul 14, 15:00 UTC | 1h 50m |
| 2026-07-14 | UAL199 | PVG → LAX | Jul 14, 12:31 UTC | Jul 14, 23:59 UTC | 11h 28m |
| 2026-07-14 | UAL199 | - | Jul 14, 06:10 UTC | Jul 15, 00:10 UTC | 17h 59m |
| 2026-07-13 | UAL198 | - | Jul 13, 20:30 UTC | Jul 14, 08:00 UTC | 11h 30m |
| 2026-07-13 | UAL198 | LAX → PVG | Jul 13, 20:31 UTC | Jul 14, 08:49 UTC | 12h 18m |
| 2026-07-13 | UAL772 | - | Jul 13, 05:05 UTC | Jul 13, 16:05 UTC | 11h 0m |
| 2026-07-13 | UAL772 | PEK → LAX | Jul 13, 04:29 UTC | Jul 13, 16:04 UTC | 11h 35m |
| 2026-07-12 | UAL771 | - | Jul 12, 07:25 UTC | Jul 12, 19:10 UTC | 11h 45m |
| 2026-07-11 | UAL353 | - | Jul 11, 23:20 UTC | Jul 12, 04:15 UTC | 4h 55m |
| 2026-07-11 | UAL2096 | - | Jul 11, 15:50 UTC | Jul 11, 21:00 UTC | 5h 10m |
| 2026-07-11 | UAL353 | - | Jul 11, 01:10 UTC | Jul 11, 06:15 UTC | 5h 5m |
| 2026-07-10 | UAL2096 | - | Jul 10, 17:25 UTC | Jul 10, 22:10 UTC | 4h 45m |
| 2026-07-09 | UAL199 | - | Jul 9, 13:15 UTC | Jul 9, 15:00 UTC | 1h 45m |
| 2026-07-09 | UAL199 | - | Jul 9, 06:35 UTC | Jul 10, 00:05 UTC | 17h 30m |
| 2026-07-08 | UAL198 | - | Jul 8, 20:30 UTC | Jul 9, 08:35 UTC | 12h 5m |
| 2026-07-08 | UAL198 | LAX → PVG | Jul 8, 20:31 UTC | Jul 9, 09:27 UTC | 12h 56m |
| 2026-07-08 | UAL153 | HKG → LAX | Jul 8, 04:55 UTC | Jul 8, 17:30 UTC | 12h 35m |
| 2026-07-08 | UAL153 | HKG → LAX | Jul 8, 01:45 UTC | Jul 8, 02:25 UTC | 40m |
| 2026-07-07 | UAL152 | LAX → HKG | Jul 7, 14:50 UTC | Jul 7, 15:05 UTC | 15m |
| 2026-07-06 | UAL152 | LAX → HKG | Jul 6, 20:15 UTC | Jul 7, 10:35 UTC | 14h 20m |
| 2026-07-05 | UAL199 | PVG → LAX | Jul 5, 12:31 UTC | Jul 5, 23:44 UTC | 11h 13m |
| 2026-07-05 | UAL199 | PVG → LAX | Jul 5, 06:30 UTC | Jul 5, 23:50 UTC | 17h 20m |
| 2026-07-04 | UAL198 | - | Jul 4, 20:25 UTC | Jul 5, 14:45 UTC | 18h 20m |
| 2026-07-04 | UAL2692 | EWR → LAX | Jul 4, 13:49 UTC | Jul 4, 18:20 UTC | 4h 31m |
| 2026-07-04 | UAL2692 | - | Jul 4, 13:35 UTC | Jul 4, 18:20 UTC | 4h 45m |
| 2026-07-03 | UAL83 | DEL → EWR | Jul 3, 18:30 UTC | Jul 3, 19:05 UTC | 35m |
| 2026-07-03 | UAL83 | DEL → EWR | Jul 3, 18:37 UTC | Jul 4, 10:09 UTC | 15h 32m |
| 2026-07-03 | UAL83 | DEL → EWR | Jul 3, 18:37 UTC | Jul 4, 09:54 UTC | 15h 17m |
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 N24979 page for operator, model, and routing details .