sensors Mode-S transponder
A18CBB
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N19951 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC
- Hex
- A18CBB
- Octal
- 50306273
- Decimal
- 10,587,323
- Country
- US
- Tail
- N19951
- Type
- B789
- Flights observed
- 212
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- 7h ago
Last known position
Country allocation
The ICAO 24-bit address A18CBB 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 |
|---|---|---|---|
| UAL820 | United Airlines | 11 | 2026-06-09 |
| UAL821 | United Airlines | 10 | 2026-06-09 |
| UAL33 | - | 9 | 2026-07-09 |
| UAL153 | United Airlines | 9 | 2026-04-23 |
| UAL152 | United Airlines | 9 | 2026-04-22 |
| UAL7 | - | 8 | 2026-07-08 |
| UAL63 | - | 8 | 2026-07-08 |
| UAL198 | - | 8 | 2026-07-09 |
| UAL6 | - | 7 | 2026-07-06 |
| UAL62 | - | 6 | 2026-07-07 |
| UAL32 | - | 6 | 2026-07-05 |
| UAL199 | - | 6 | 2026-07-10 |
| UAL178 | United Airlines | 5 | 2026-05-15 |
| UAL842 | - | 4 | 2026-07-05 |
| UAL806 | - | 4 | 2026-07-01 |
| UAL761 | United Airlines | 4 | 2026-05-18 |
| UAL760 | United Airlines | 4 | 2026-05-18 |
| UAL26 | United Airlines | 4 | 2026-05-09 |
| UAL182 | United Airlines | 4 | 2026-05-13 |
| UAL181 | United Airlines | 4 | 2026-05-14 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-13 | UAL949 | - | Jul 13, 12:30 UTC | Jul 13, 23:00 UTC | 10h 30m |
| 2026-07-13 | UAL948 | SFO → LHR | Jul 13, 00:40 UTC | Jul 13, 10:05 UTC | 9h 25m |
| 2026-07-12 | UAL870 | - | Jul 12, 01:35 UTC | Jul 12, 02:40 UTC | 1h 5m |
| 2026-07-12 | UAL870 | SYD → SFO | Jul 12, 01:35 UTC | Jul 12, 14:38 UTC | 13h 3m |
| 2026-07-11 | UAL839 | - | Jul 11, 07:40 UTC | Jul 11, 21:50 UTC | 14h 10m |
| 2026-07-10 | UAL199 | - | Jul 10, 13:05 UTC | Jul 10, 14:45 UTC | 1h 40m |
| 2026-07-10 | UAL199 | PVG → LAX | Jul 10, 12:31 UTC | Jul 11, 00:42 UTC | 12h 11m |
| 2026-07-10 | UAL199 | - | Jul 10, 06:20 UTC | Jul 11, 00:50 UTC | 18h 30m |
| 2026-07-09 | UAL198 | - | Jul 9, 20:25 UTC | Jul 9, 21:35 UTC | 1h 10m |
| 2026-07-09 | UAL198 | LAX → PVG | Jul 9, 20:31 UTC | Jul 10, 09:11 UTC | 12h 40m |
| 2026-07-09 | UAL33 | - | Jul 9, 08:10 UTC | Jul 9, 17:40 UTC | 9h 30m |
| 2026-07-08 | UAL7 | - | Jul 8, 16:00 UTC | Jul 9, 05:00 UTC | 13h 0m |
| 2026-07-08 | UAL63 | - | Jul 8, 01:10 UTC | Jul 8, 02:45 UTC | 1h 35m |
| 2026-07-08 | UAL63 | GRU → IAH | Jul 8, 01:11 UTC | Jul 8, 10:27 UTC | 9h 16m |
| 2026-07-07 | UAL62 | - | Jul 7, 00:15 UTC | Jul 7, 00:35 UTC | 20m |
| 2026-07-07 | UAL62 | IAH → GRU | Jul 7, 00:13 UTC | Jul 7, 09:12 UTC | 8h 59m |
| 2026-07-06 | UAL6 | - | Jul 6, 08:05 UTC | Jul 6, 19:15 UTC | 11h 10m |
| 2026-07-05 | UAL32 | - | Jul 5, 18:10 UTC | Jul 6, 04:50 UTC | 10h 40m |
| 2026-07-05 | UAL842 | - | Jul 5, 00:10 UTC | Jul 5, 00:45 UTC | 35m |
| 2026-07-04 | UAL842 | SYD → LAX | Jul 4, 23:51 UTC | Jul 5, 13:18 UTC | 13h 27m |
| 2026-07-04 | UAL863 | SFO → SYD | Jul 4, 06:31 UTC | Jul 4, 20:48 UTC | 14h 17m |
| 2026-07-04 | UAL863 | SFO → SYD | Jul 4, 06:35 UTC | Jul 4, 21:00 UTC | 14h 25m |
| 2026-07-03 | UAL969 | AMS → SFO | Jul 3, 13:16 UTC | Jul 3, 23:46 UTC | 10h 30m |
| 2026-07-03 | UAL969 | - | Jul 3, 13:25 UTC | Jul 3, 14:55 UTC | 1h 30m |
| 2026-07-02 | UAL968 | - | Jul 2, 23:05 UTC | Jul 3, 08:30 UTC | 9h 25m |
| 2026-07-02 | UAL892 | - | Jul 2, 08:20 UTC | Jul 2, 18:20 UTC | 10h 0m |
| 2026-07-01 | UAL893 | - | Jul 1, 18:15 UTC | Jul 2, 06:20 UTC | 12h 5m |
| 2026-07-01 | UAL806 | - | Jul 1, 02:45 UTC | Jul 1, 12:50 UTC | 10h 5m |
| 2026-06-30 | UAL805 | SFO → ICN | Jun 30, 07:50 UTC | Jun 30, 19:35 UTC | 11h 45m |
| 2026-06-29 | UAL28 | - | Jun 29, 14:29 UTC | Jun 30, 04:30 UTC | 14h 1m |
| 2026-06-28 | UAL29 | - | Jun 28, 18:55 UTC | Jun 29, 08:50 UTC | 13h 55m |
| 2026-06-28 | UAL29 | SFO → SIN | Jun 28, 18:35 UTC | Jun 29, 10:38 UTC | 16h 3m |
| 2026-06-28 | UAL806 | ICN → SFO | Jun 28, 02:56 UTC | Jun 28, 12:42 UTC | 9h 46m |
| 2026-06-28 | UAL806 | - | Jun 28, 02:44 UTC | Jun 28, 04:20 UTC | 1h 35m |
| 2026-06-27 | UAL805 | SFO → ICN | Jun 27, 07:55 UTC | Jun 27, 19:34 UTC | 11h 40m |
| 2026-06-26 | UAL1757 | IAD → SFO | Jun 26, 22:44 UTC | Jun 27, 03:55 UTC | 5h 10m |
| 2026-06-26 | UAL1849 | MCO → EWR | Jun 26, 15:45 UTC | Jun 26, 20:00 UTC | 4h 15m |
| 2026-06-26 | UAL806 | ICN → SFO | Jun 26, 02:44 UTC | Jun 26, 12:29 UTC | 9h 45m |
| 2026-06-25 | UAL805 | SFO → ICN | Jun 25, 07:49 UTC | Jun 25, 19:24 UTC | 11h 35m |
| 2026-06-24 | UAL1757 | - | Jun 24, 22:29 UTC | Jun 25, 03:40 UTC | 5h 10m |
| 2026-06-23 | UAL2274 | SFO → IAD | Jun 23, 20:10 UTC | Jun 24, 00:25 UTC | 4h 15m |
| 2026-06-23 | UAL1147 | IAD → SFO | Jun 23, 12:35 UTC | Jun 23, 17:50 UTC | 5h 15m |
| 2026-06-22 | UAL2274 | SFO → IAD | Jun 22, 20:24 UTC | Jun 23, 00:39 UTC | 4h 15m |
| 2026-06-22 | UAL1147 | - | Jun 22, 12:54 UTC | Jun 22, 18:15 UTC | 5h 20m |
| 2026-06-21 | UAL2023 | CPT → IAD | Jun 21, 18:20 UTC | Jun 22, 09:30 UTC | 15h 10m |
| 2026-06-20 | UAL1011 | IAD → CPT | Jun 20, 22:39 UTC | Jun 21, 12:40 UTC | 14h 0m |
| 2026-06-20 | UAL1849 | MCO → EWR | Jun 20, 15:39 UTC | Jun 20, 19:55 UTC | 4h 15m |
| 2026-06-19 | UAL892 | ICN → SFO | Jun 19, 08:14 UTC | Jun 19, 18:59 UTC | 10h 45m |
| 2026-06-18 | UAL893 | SFO → ICN | Jun 18, 18:35 UTC | Jun 19, 05:45 UTC | 11h 9m |
| 2026-06-18 | UAL61 | MEL → SFO | Jun 18, 01:09 UTC | Jun 18, 14:59 UTC | 13h 50m |
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 N19951 page for operator, model, and routing details .