sensors Mode-S transponder
51104D
ICAO 24-bit transponder address · allocated to Estonia
Currently assigned to ES-PCO · CESSNA 172 Skyhawk
- Hex
- 51104D
- Octal
- 24210115
- Decimal
- 5,312,589
- Country
- EE
- Tail
- ES-PCO
- Type
- C172
- Flights observed
- 27
- Distinct callsigns
- 1
- Country
- EE
- Last broadcast
- 1h ago
Last known position
Country allocation
The ICAO 24-bit address 51104D falls within the block assigned to Estonia (EE) by ICAO Annex 10, Volume III. Every aircraft registered in Estonia 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 |
|---|---|---|---|
| ESPCO | - | 27 | 2026-07-14 |
Recent flights last 27
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-14 | ESPCO | - | Jul 14, 07:50 UTC | Jul 14, 08:55 UTC | 1h 5m |
| 2026-07-13 | ESPCO | TLL → TLL | Jul 13, 07:20 UTC | Jul 13, 09:35 UTC | 2h 15m |
| 2026-07-01 | ESPCO | TLL → TLL | Jul 1, 07:30 UTC | Jul 1, 10:40 UTC | 3h 10m |
| 2026-06-30 | ESPCO | TLL → TLL | Jun 30, 09:30 UTC | Jun 30, 10:40 UTC | 1h 10m |
| 2026-06-30 | ESPCO | TLL → TLL | Jun 30, 06:55 UTC | Jun 30, 08:10 UTC | 1h 15m |
| 2026-06-28 | ESPCO | TLL → TLL | Jun 28, 06:59 UTC | Jun 28, 07:34 UTC | 35m |
| 2026-06-27 | ESPCO | TLL → TLL | Jun 27, 08:39 UTC | Jun 27, 11:59 UTC | 3h 20m |
| 2026-06-23 | ESPCO | TLL → TLL | Jun 23, 07:09 UTC | Jun 23, 10:29 UTC | 3h 20m |
| 2026-06-22 | ESPCO | TLL → TLL | Jun 22, 07:04 UTC | Jun 22, 10:05 UTC | 3h 0m |
| 2026-06-20 | ESPCO | TLL → TLL | Jun 20, 07:19 UTC | Jun 20, 10:25 UTC | 3h 5m |
| 2026-06-19 | ESPCO | - | Jun 19, 10:09 UTC | Jun 19, 10:50 UTC | 40m |
| 2026-06-19 | ESPCO | - | Jun 19, 07:14 UTC | Jun 19, 08:24 UTC | 1h 10m |
| 2026-06-18 | ESPCO | TLL → TLL | Jun 18, 07:05 UTC | Jun 18, 10:20 UTC | 3h 15m |
| 2026-06-11 | ESPCO | TLL → TLL | Jun 11, 07:20 UTC | Jun 11, 10:30 UTC | 3h 10m |
| 2026-06-08 | ESPCO | TLL → TLL | Jun 8, 07:35 UTC | Jun 8, 10:35 UTC | 3h 0m |
| 2026-06-07 | ESPCO | TLL → TLL | Jun 7, 07:15 UTC | Jun 7, 10:20 UTC | 3h 5m |
| 2026-06-05 | ESPCO | TLL → TLL | Jun 5, 07:25 UTC | Jun 5, 08:50 UTC | 1h 25m |
| 2026-06-04 | ESPCO | - | Jun 4, 09:20 UTC | Jun 4, 11:50 UTC | 2h 30m |
| 2026-06-02 | ESPCO | TLL → TLL | Jun 2, 08:30 UTC | Jun 2, 10:50 UTC | 2h 20m |
| 2026-06-01 | ESPCO | TLL → TLL | Jun 1, 10:25 UTC | Jun 1, 13:15 UTC | 2h 50m |
| 2026-05-30 | ESPCO | TLL → TLL | May 30, 07:15 UTC | May 30, 10:50 UTC | 3h 35m |
| 2026-05-29 | ESPCO | TLL → TLL | May 29, 07:00 UTC | May 29, 10:05 UTC | 3h 5m |
| 2026-05-19 | ESPCO | TLL → TLL | May 19, 12:40 UTC | May 19, 13:20 UTC | 40m |
| 2026-05-06 | ESPCO | TLL → TLL | May 6, 07:20 UTC | May 6, 08:35 UTC | 1h 15m |
| 2026-05-01 | ESPCO | TLL → TLL | May 1, 05:40 UTC | May 1, 06:45 UTC | 1h 5m |
| 2026-04-13 | ESPCO | - | Apr 13, 08:20 UTC | Apr 13, 09:00 UTC | 40m |
| 2026-04-13 | ESPCO | TLL → TLL | Apr 13, 08:10 UTC | Apr 13, 09:00 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 ES-PCO page for operator, model, and routing details .