sensors Mode-S transponder
A65D21
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N509U · TECNAM Twenty-Ten · operated by ALBA LEASING SERVICES LLC
- Hex
- A65D21
- Octal
- 51456441
- Decimal
- 10,902,817
- Country
- US
- Tail
- N509U
- Type
- TWEN
- Flights observed
- 57
- Distinct callsigns
- 1
- Country
- US
- Last broadcast
- 2d ago
Last known position
Country allocation
The ICAO 24-bit address A65D21 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 1 distinct
| Callsign | Airline | Flights | Last seen |
|---|---|---|---|
| N509U | - | 57 | 2026-07-12 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-12 | N509U | - | Jul 12, 15:55 UTC | Jul 12, 16:15 UTC | 20m |
| 2026-07-11 | N509U | ACT → ACT | Jul 11, 15:00 UTC | Jul 11, 16:15 UTC | 1h 15m |
| 2026-07-10 | N509U | ACT → ACT | Jul 10, 20:30 UTC | Jul 10, 21:30 UTC | 1h 1m |
| 2026-07-10 | N509U | ACT → ACT | Jul 10, 17:35 UTC | Jul 10, 19:00 UTC | 1h 25m |
| 2026-07-09 | N509U | ACT → ACT | Jul 9, 16:25 UTC | Jul 9, 17:45 UTC | 1h 20m |
| 2026-06-30 | N509U | ACT → ACT | Jun 30, 17:15 UTC | Jun 30, 18:50 UTC | 1h 35m |
| 2026-06-29 | N509U | - | Jun 29, 16:59 UTC | Jun 29, 19:35 UTC | 2h 35m |
| 2026-06-26 | N509U | - | Jun 26, 14:35 UTC | Jun 26, 16:09 UTC | 1h 35m |
| 2026-06-25 | N509U | - | Jun 25, 18:39 UTC | Jun 25, 19:59 UTC | 1h 20m |
| 2026-06-25 | N509U | ACT → ACT | Jun 25, 14:09 UTC | Jun 25, 15:29 UTC | 1h 20m |
| 2026-06-25 | N509U | AUS → ACT | Jun 25, 03:50 UTC | Jun 25, 04:35 UTC | 45m |
| 2026-06-25 | N509U | - | Jun 25, 02:45 UTC | Jun 25, 03:44 UTC | 1h 0m |
| 2026-06-24 | N509U | ACT → ACT | Jun 24, 16:40 UTC | Jun 24, 17:29 UTC | 50m |
| 2026-06-24 | N509U | - | Jun 24, 14:04 UTC | Jun 24, 15:09 UTC | 1h 5m |
| 2026-06-24 | N509U | ACT → ACT | Jun 24, 02:30 UTC | Jun 24, 03:55 UTC | 1h 25m |
| 2026-06-23 | N509U | ACT → ACT | Jun 23, 20:29 UTC | Jun 23, 21:45 UTC | 1h 15m |
| 2026-06-23 | N509U | ACT → ACT | Jun 23, 17:30 UTC | Jun 23, 18:50 UTC | 1h 20m |
| 2026-06-22 | N509U | ACT → ACT | Jun 22, 20:55 UTC | Jun 22, 22:24 UTC | 1h 30m |
| 2026-06-22 | N509U | - | Jun 22, 17:29 UTC | Jun 22, 18:04 UTC | 35m |
| 2026-06-22 | N509U | - | Jun 22, 14:29 UTC | Jun 22, 15:14 UTC | 45m |
| 2026-06-19 | N509U | ACT → ACT | Jun 19, 00:24 UTC | Jun 19, 01:15 UTC | 50m |
| 2026-06-18 | N509U | - | Jun 18, 21:50 UTC | Jun 18, 23:00 UTC | 1h 10m |
| 2026-06-18 | N509U | ACT → ACT | Jun 18, 16:35 UTC | Jun 18, 17:00 UTC | 25m |
| 2026-06-16 | N509U | - | Jun 16, 16:15 UTC | Jun 16, 16:45 UTC | 30m |
| 2026-06-12 | N509U | - | Jun 12, 14:50 UTC | Jun 12, 15:40 UTC | 50m |
| 2026-06-08 | N509U | - | Jun 8, 17:50 UTC | Jun 8, 18:30 UTC | 40m |
| 2026-06-08 | N509U | - | Jun 8, 15:00 UTC | Jun 8, 15:55 UTC | 55m |
| 2026-05-16 | N509U | - | May 16, 20:05 UTC | May 16, 21:50 UTC | 1h 45m |
| 2026-05-16 | N509U | - | May 16, 18:05 UTC | May 16, 19:20 UTC | 1h 15m |
| 2026-05-15 | N509U | - | May 15, 21:35 UTC | May 15, 22:40 UTC | 1h 5m |
| 2026-05-12 | N509U | - | May 12, 18:10 UTC | May 12, 19:00 UTC | 50m |
| 2026-05-11 | N509U | - | May 11, 14:40 UTC | May 11, 15:45 UTC | 1h 5m |
| 2026-05-05 | N509U | - | May 5, 23:10 UTC | May 5, 23:45 UTC | 35m |
| 2026-05-04 | N509U | - | May 4, 20:20 UTC | May 4, 21:45 UTC | 1h 25m |
| 2026-05-02 | N509U | - | May 2, 15:55 UTC | May 2, 16:55 UTC | 1h 0m |
| 2026-04-27 | N509U | - | Apr 27, 21:55 UTC | Apr 27, 22:35 UTC | 40m |
| 2026-04-27 | N509U | - | Apr 27, 18:10 UTC | Apr 27, 18:30 UTC | 20m |
| 2026-04-26 | N509U | - | Apr 26, 22:35 UTC | Apr 26, 23:40 UTC | 1h 5m |
| 2026-04-25 | N509U | - | Apr 25, 19:30 UTC | Apr 25, 20:25 UTC | 55m |
| 2026-04-25 | N509U | - | Apr 25, 15:35 UTC | Apr 25, 16:55 UTC | 1h 20m |
| 2026-04-25 | N509U | - | Apr 25, 00:35 UTC | Apr 25, 00:55 UTC | 20m |
| 2026-04-24 | N509U | - | Apr 24, 21:30 UTC | Apr 24, 23:00 UTC | 1h 30m |
| 2026-04-24 | N509U | - | Apr 24, 19:15 UTC | Apr 24, 20:15 UTC | 1h 0m |
| 2026-04-24 | N509U | - | Apr 24, 00:15 UTC | Apr 24, 01:35 UTC | 1h 20m |
| 2026-04-23 | N509U | - | Apr 23, 21:00 UTC | Apr 23, 22:00 UTC | 1h 0m |
| 2026-04-23 | N509U | - | Apr 23, 18:45 UTC | Apr 23, 19:40 UTC | 55m |
| 2026-04-23 | N509U | - | Apr 23, 15:00 UTC | Apr 23, 15:20 UTC | 20m |
| 2026-04-23 | N509U | - | Apr 23, 01:30 UTC | Apr 23, 02:15 UTC | 45m |
| 2026-04-22 | N509U | - | Apr 22, 21:20 UTC | Apr 22, 21:30 UTC | 10m |
| 2026-04-22 | N509U | - | Apr 22, 18:45 UTC | Apr 22, 19:35 UTC | 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 N509U page for operator, model, and routing details .