sensors Mode-S transponder
A254FF
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N24988 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A254FF
- Octal
- 50452377
- Decimal
- 10,638,591
- Country
- US
- Tail
- N24988
- Type
- B789
- Flights observed
- 101
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 54m ago
Current position
Country allocation
The ICAO 24-bit address A254FF 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 |
|---|---|---|---|
| UAL1011 | United Airlines | 9 | 2026-05-31 |
| UAL2023 | United Airlines | 8 | 2026-06-01 |
| UAL893 | United Airlines | 6 | 2026-05-01 |
| UAL863 | United Airlines | 6 | 2026-04-30 |
| UAL187 | United Airlines | 6 | 2026-05-19 |
| UAL892 | United Airlines | 5 | 2026-05-02 |
| UAL60 | United Airlines | 5 | 2026-05-03 |
| UAL1849 | United Airlines | 5 | 2026-05-23 |
| UAL1757 | United Airlines | 5 | 2026-04-27 |
| UAL806 | United Airlines | 4 | 2026-05-06 |
| UAL805 | United Airlines | 4 | 2026-05-05 |
| UAL61 | United Airlines | 4 | 2026-05-04 |
| UAL188 | United Airlines | 4 | 2026-05-19 |
| UAL870 | United Airlines | 3 | 2026-05-01 |
| UAL79 | United Airlines | 3 | 2026-05-14 |
| UAL198 | United Airlines | 3 | 2026-05-10 |
| UAL1593 | United Airlines | 3 | 2026-05-22 |
| UAL78 | United Airlines | 2 | 2026-05-18 |
| UAL7 | United Airlines | 2 | 2026-05-17 |
| UAL199 | United Airlines | 2 | 2026-05-10 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-06-03 | UAL2397 | EWR → PDX | Jun 3, 04:20 UTC | Jun 3, 07:45 UTC | 3h 25m |
| 2026-06-02 | UAL2238 | IAH → SFO | Jun 2, 20:50 UTC | Jun 3, 01:40 UTC | 4h 50m |
| 2026-06-01 | UAL2222 | IAD → CPT | Jun 1, 18:25 UTC | Jun 2, 09:35 UTC | 15h 10m |
| 2026-06-01 | UAL2023 | BOS → ORD | Jun 1, 00:45 UTC | Jun 1, 01:05 UTC | 20m |
| 2026-05-31 | UAL2023 | BOS → ORD | May 31, 20:00 UTC | May 31, 20:15 UTC | 15m |
| 2026-05-31 | UAL1011 | MCI → SFO | May 31, 12:35 UTC | May 31, 12:50 UTC | 15m |
| 2026-05-30 | UAL1011 | MCI → SFO | May 30, 22:51 UTC | May 31, 12:42 UTC | 13h 51m |
| 2026-05-30 | UAL1011 | MCI → SFO | May 30, 22:50 UTC | May 31, 00:30 UTC | 1h 40m |
| 2026-05-29 | UAL2023 | BOS → ORD | May 29, 18:21 UTC | May 30, 09:01 UTC | 14h 40m |
| 2026-05-29 | UAL2023 | BOS → ORD | May 29, 18:05 UTC | May 29, 18:25 UTC | 20m |
| 2026-05-28 | UAL1011 | MCI → SFO | May 28, 23:40 UTC | May 29, 13:15 UTC | 13h 35m |
| 2026-05-26 | UAL2023 | BOS → ORD | May 26, 18:05 UTC | May 27, 09:05 UTC | 15h 1m |
| 2026-05-25 | UAL1011 | MCI → SFO | May 25, 22:55 UTC | May 26, 12:50 UTC | 13h 55m |
| 2026-05-24 | UAL2023 | BOS → ORD | May 24, 18:21 UTC | May 25, 09:26 UTC | 15h 5m |
| 2026-05-24 | UAL2023 | BOS → ORD | May 24, 18:15 UTC | May 25, 09:30 UTC | 15h 15m |
| 2026-05-24 | UAL1011 | MCI → SFO | May 24, 13:05 UTC | May 24, 13:20 UTC | 15m |
| 2026-05-23 | UAL1011 | MCI → SFO | May 23, 23:45 UTC | May 24, 01:30 UTC | 1h 45m |
| 2026-05-23 | UAL1849 | MCO → EWR | May 23, 15:35 UTC | May 23, 20:10 UTC | 4h 36m |
| 2026-05-22 | UAL1593 | LGA → DEN | May 22, 14:32 UTC | May 22, 19:30 UTC | 4h 58m |
| 2026-05-22 | UAL1593 | LGA → DEN | May 22, 14:25 UTC | May 22, 19:35 UTC | 5h 10m |
| 2026-05-21 | UAL2480 | BOS → SFO | May 21, 21:50 UTC | May 22, 02:25 UTC | 4h 35m |
| 2026-05-21 | UAL1593 | LGA → DEN | May 21, 13:50 UTC | May 21, 18:55 UTC | 5h 5m |
| 2026-05-19 | UAL187 | JNB → EWR | May 19, 20:19 UTC | May 20, 12:04 UTC | 15h 45m |
| 2026-05-19 | UAL187 | JNB → EWR | May 19, 20:05 UTC | May 20, 12:10 UTC | 16h 6m |
| 2026-05-19 | UAL187 | JNB → EWR | May 19, 20:19 UTC | May 20, 12:07 UTC | 15h 48m |
| 2026-05-19 | UAL188 | EWR → JNB | May 19, 02:15 UTC | May 19, 15:55 UTC | 13h 40m |
| 2026-05-18 | UAL78 | NRT → EWR | May 18, 08:45 UTC | May 18, 20:50 UTC | 12h 4m |
| 2026-05-17 | UAL7 | IAH → NRT | May 17, 15:32 UTC | May 18, 04:13 UTC | 12h 41m |
| 2026-05-17 | UAL7 | IAH → NRT | May 17, 15:45 UTC | May 18, 04:11 UTC | 12h 25m |
| 2026-05-17 | UAL63 | GRU → IAH | May 17, 01:05 UTC | May 17, 10:25 UTC | 9h 20m |
| 2026-05-16 | UAL62 | IAH → GRU | May 16, 00:00 UTC | May 16, 08:36 UTC | 8h 36m |
| 2026-05-15 | UAL6 | NRT → IAH | May 15, 08:15 UTC | May 15, 19:50 UTC | 11h 34m |
| 2026-05-14 | UAL79 | EWR → NRT | May 14, 15:40 UTC | May 15, 04:10 UTC | 12h 30m |
| 2026-05-13 | UAL187 | JNB → EWR | May 13, 20:05 UTC | May 14, 11:45 UTC | 15h 40m |
| 2026-05-13 | UAL187 | JNB → EWR | May 13, 20:19 UTC | May 14, 11:33 UTC | 15h 14m |
| 2026-05-13 | UAL188 | EWR → JNB | May 13, 02:05 UTC | May 13, 16:05 UTC | 14h 0m |
| 2026-05-12 | UAL78 | NRT → EWR | May 12, 09:00 UTC | May 12, 20:50 UTC | 11h 50m |
| 2026-05-11 | UAL32 | LAX → NRT | May 11, 18:15 UTC | May 12, 04:50 UTC | 10h 35m |
| 2026-05-10 | UAL199 | PVG → LAX | May 10, 06:50 UTC | May 10, 23:00 UTC | 16h 10m |
| 2026-05-10 | UAL199 | PVG → LAX | May 10, 01:50 UTC | May 10, 23:00 UTC | 21h 10m |
| 2026-05-10 | UAL198 | LAX → PVG | May 10, 00:09 UTC | May 10, 23:00 UTC | 22h 50m |
| 2026-05-09 | UAL198 | LAX → PVG | May 9, 20:08 UTC | May 10, 09:35 UTC | 13h 27m |
| 2026-05-09 | UAL198 | LAX → PVG | May 9, 20:15 UTC | May 10, 14:34 UTC | 18h 20m |
| 2026-05-09 | UAL33 | NRT → LAX | May 9, 08:05 UTC | May 9, 17:25 UTC | 9h 20m |
| 2026-05-08 | UAL79 | EWR → NRT | May 8, 16:05 UTC | May 8, 23:10 UTC | 7h 5m |
| 2026-05-08 | UAL79 | EWR → NRT | May 8, 15:57 UTC | May 9, 05:27 UTC | 13h 30m |
| 2026-05-07 | UAL187 | JNB → EWR | May 7, 20:05 UTC | May 8, 11:44 UTC | 15h 40m |
| 2026-05-07 | UAL188 | EWR → JNB | May 7, 02:14 UTC | May 7, 15:56 UTC | 13h 42m |
| 2026-05-07 | UAL188 | EWR → JNB | May 7, 02:05 UTC | May 7, 02:45 UTC | 40m |
| 2026-05-06 | UAL713 | ORD → DEL | May 6, 17:35 UTC | May 6, 22:10 UTC | 4h 35m |
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 N24988 page for operator, model, and routing details .