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
- 235
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- Jul 26, 20:55 UTC
Current 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 |
| UAL153 | United Airlines | 11 | 2026-07-24 |
| UAL152 | - | 11 | 2026-07-23 |
| UAL821 | United Airlines | 10 | 2026-06-09 |
| UAL33 | - | 9 | 2026-07-09 |
| UAL198 | United Airlines | 9 | 2026-07-24 |
| UAL7 | - | 8 | 2026-07-08 |
| UAL63 | - | 8 | 2026-07-08 |
| UAL6 | - | 7 | 2026-07-06 |
| UAL199 | United Airlines | 7 | 2026-07-25 |
| UAL62 | - | 6 | 2026-07-07 |
| UAL32 | - | 6 | 2026-07-05 |
| UAL29 | - | 5 | 2026-07-16 |
| UAL178 | United Airlines | 5 | 2026-05-15 |
| UAL842 | - | 4 | 2026-07-05 |
| UAL839 | United Airlines | 4 | 2026-07-26 |
| UAL806 | - | 4 | 2026-07-01 |
| UAL761 | United Airlines | 4 | 2026-05-18 |
| UAL760 | United Airlines | 4 | 2026-05-18 |
| UAL60 | - | 4 | 2026-07-17 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-26 | UAL839 | LAX → SYD | Jul 26, 06:10 UTC | Jul 26, 20:40 UTC | 14h 31m |
| 2026-07-25 | UAL199 | PVG → LAX | Jul 25, 06:05 UTC | Jul 26, 00:35 UTC | 18h 30m |
| 2026-07-24 | UAL198 | LAX → PVG | Jul 24, 20:50 UTC | Jul 25, 15:35 UTC | 18h 45m |
| 2026-07-24 | UAL153 | HKG → LAX | Jul 24, 04:55 UTC | Jul 24, 18:10 UTC | 13h 15m |
| 2026-07-24 | UAL153 | HKG → LAX | Jul 24, 02:25 UTC | Jul 24, 02:40 UTC | 15m |
| 2026-07-23 | UAL152 | - | Jul 23, 13:10 UTC | Jul 23, 13:25 UTC | 15m |
| 2026-07-22 | UAL152 | - | Jul 22, 20:20 UTC | Jul 23, 10:00 UTC | 13h 40m |
| 2026-07-22 | UAL353J | EWR → LAX | Jul 22, 02:34 UTC | Jul 22, 07:16 UTC | 4h 42m |
| 2026-07-22 | UAL353J | - | Jul 22, 02:20 UTC | Jul 22, 05:25 UTC | 3h 5m |
| 2026-07-21 | UAL123 | ANC → ORD | Jul 21, 07:00 UTC | Jul 21, 15:05 UTC | 8h 5m |
| 2026-07-20 | UAL122 | IAD → LHR | Jul 20, 14:10 UTC | Jul 20, 20:25 UTC | 6h 15m |
| 2026-07-19 | UAL3028 | GCM → EWR | Jul 19, 15:45 UTC | Jul 19, 16:35 UTC | 50m |
| 2026-07-18 | UAL713 | - | Jul 18, 19:10 UTC | Jul 19, 00:25 UTC | 5h 15m |
| 2026-07-18 | UAL61 | - | Jul 18, 01:20 UTC | Jul 18, 15:25 UTC | 14h 6m |
| 2026-07-17 | UAL60 | SFO → MEL | Jul 17, 07:41 UTC | Jul 17, 22:44 UTC | 15h 3m |
| 2026-07-17 | UAL60 | - | Jul 17, 07:44 UTC | Jul 17, 20:44 UTC | 13h 0m |
| 2026-07-16 | UAL28 | - | Jul 16, 14:45 UTC | Jul 17, 04:44 UTC | 14h 0m |
| 2026-07-16 | UAL29 | - | Jul 16, 10:15 UTC | Jul 16, 10:29 UTC | 15m |
| 2026-07-15 | UAL29 | SFO → SIN | Jul 15, 18:45 UTC | Jul 16, 10:28 UTC | 15h 43m |
| 2026-07-15 | UAL29 | - | Jul 15, 18:50 UTC | Jul 16, 09:05 UTC | 14h 15m |
| 2026-07-15 | UAL114 | - | Jul 15, 07:20 UTC | Jul 15, 15:10 UTC | 7h 50m |
| 2026-07-15 | UAL114 | PPT → SFO | Jul 15, 07:30 UTC | Jul 15, 15:05 UTC | 7h 35m |
| 2026-07-14 | UAL115 | SFO → PPT | Jul 14, 20:55 UTC | Jul 15, 04:45 UTC | 7h 49m |
| 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 |
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 .