Apparatus

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sensors Mode-S transponder

4521CF

ICAO 24-bit transponder address · allocated to Bulgaria

Hex
4521CF
Octal
21220717
Decimal
4,530,639
Country
BG
No current signal · last broadcast 3d ago
Flights observed
134
Distinct callsigns
20
Country
BG
Last broadcast
3d ago

Last known position

Most recent position reported by Mode-S 4521CF.

Country allocation

The ICAO 24-bit address 4521CF falls within the block assigned to Bulgaria (BG) by ICAO Annex 10, Volume III. Every aircraft registered in Bulgaria 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
AEZ7810 - 5 2026-07-01
AEZ70MH Aerial Transit Company 5 2026-05-11
AEZ49KF Aerial Transit Company 5 2026-06-20
AEZ44LG - 5 2026-07-05
AEZ2617 - 5 2026-06-30
AEZ88LL Aerial Transit Company 4 2026-06-15
AEZ2347 Aerial Transit Company 4 2026-06-07
AEZ155Z - 4 2026-06-24
AEZ139V - 4 2026-06-19
AEZ7117 - 3 2026-06-16
AEZ569P Aerial Transit Company 3 2026-05-24
AEZ318W Aerial Transit Company 3 2026-05-18
AEZ2367 Aerial Transit Company 3 2026-05-25
AEZ2363 Aerial Transit Company 3 2026-06-15
AEZ2349 Aerial Transit Company 3 2026-05-01
AEZ12RG Aerial Transit Company 3 2026-04-27
AEZ11LJ Aerial Transit Company 3 2026-06-20
AEZ833J Aerial Transit Company 2 2026-06-29
AEZ8094 - 2 2026-07-06
AEZ8041 - 2 2026-07-03

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-11 AEZ385Z OLB → LIN Jul 11, 19:25 UTCJul 11, 20:10 UTC45m
2026-07-06 AEZ14UJ - Jul 6, 15:10 UTCJul 6, 16:05 UTC55m
2026-07-06 AEZ47LG - Jul 6, 10:40 UTCJul 6, 11:35 UTC55m
2026-07-06 AEZ8094 - Jul 6, 08:20 UTCJul 6, 09:20 UTC1h 0m
2026-07-05 AEZ14UJ - Jul 5, 15:45 UTCJul 5, 16:45 UTC1h 0m
2026-07-05 AEZ47LG - Jul 5, 11:00 UTCJul 5, 12:10 UTC1h 10m
2026-07-05 AEZ44LG - Jul 5, 06:30 UTCJul 5, 07:25 UTC55m
2026-07-04 AEZ112X - Jul 4, 11:15 UTCJul 4, 11:40 UTC25m
2026-07-04 AEZ2330 - Jul 4, 04:20 UTCJul 4, 05:00 UTC40m
2026-07-03 AEZ8041 - Jul 3, 06:20 UTCJul 3, 07:15 UTC55m
2026-07-01 AEZ7810 - Jul 1, 05:15 UTCJul 1, 05:50 UTC35m
2026-06-30 AEZ7810 OLB → FCO Jun 30, 05:20 UTCJun 30, 05:45 UTC25m
2026-06-30 AEZ2617 - Jun 30, 00:09 UTCJun 30, 00:35 UTC25m
2026-06-29 AEZ7816 OLB → FCO Jun 29, 22:44 UTCJun 29, 23:09 UTC25m
2026-06-29 AEZ833J LIN → OLB Jun 29, 20:30 UTCJun 29, 21:24 UTC55m
2026-06-28 AEZ2617 - Jun 28, 20:25 UTCJun 28, 20:59 UTC35m
2026-06-28 AEZ7816 OLB → FCO Jun 28, 18:14 UTCJun 28, 18:49 UTC35m
2026-06-28 AEZ7811 FCO → OLB Jun 28, 05:49 UTCJun 28, 06:24 UTC35m
2026-06-27 AEZ7811 FCO → OLB Jun 27, 05:55 UTCJun 27, 06:19 UTC25m
2026-06-24 AEZ155Z - Jun 24, 08:04 UTCJun 24, 08:49 UTC45m
2026-06-24 AEZ516C - Jun 24, 05:05 UTCJun 24, 06:04 UTC1h 0m
2026-06-23 AEZ7817 FCO → OLB Jun 23, 19:10 UTCJun 23, 19:39 UTC30m
2026-06-23 AEZ418P - Jun 23, 17:39 UTCJun 23, 18:10 UTC30m
2026-06-23 AEZ11GR - Jun 23, 11:19 UTCJun 23, 11:59 UTC40m
2026-06-23 AEZ100N FCO → CAG Jun 23, 05:24 UTCJun 23, 06:04 UTC40m
2026-06-22 AEZ2575 - Jun 22, 20:44 UTCJun 22, 22:10 UTC1h 25m
2026-06-22 AEZ2575 IBZ → IBZ Jun 22, 16:34 UTCJun 22, 17:00 UTC25m
2026-06-22 AEZ2574 - Jun 22, 13:29 UTCJun 22, 15:05 UTC1h 35m
2026-06-22 AEZ419P - Jun 22, 05:54 UTCJun 22, 06:10 UTC15m
2026-06-20 AEZ49KF CAG → LIN Jun 20, 18:34 UTCJun 20, 19:29 UTC55m
2026-06-20 AEZ11LJ FCO → CAG Jun 20, 16:29 UTCJun 20, 16:59 UTC30m
2026-06-20 AEZ131R FCO → OLB Jun 20, 11:54 UTCJun 20, 12:19 UTC25m
2026-06-19 AEZ7340 - Jun 19, 18:49 UTCJun 19, 19:29 UTC40m
2026-06-19 AEZ833J LIN → OLB Jun 19, 16:49 UTCJun 19, 17:34 UTC45m
2026-06-19 AEZ131R FCO → OLB Jun 19, 11:39 UTCJun 19, 12:14 UTC35m
2026-06-19 AEZ7812 OLB → FCO Jun 19, 09:34 UTCJun 19, 09:59 UTC25m
2026-06-19 AEZ139V - Jun 19, 07:29 UTCJun 19, 08:04 UTC35m
2026-06-18 AEZ311L OLB → FCO Jun 18, 13:55 UTCJun 18, 14:25 UTC30m
2026-06-17 AEZ385Z OLB → LIN Jun 17, 17:20 UTCJun 17, 18:10 UTC50m
2026-06-17 AEZ2630 OLB → LIN Jun 17, 12:05 UTCJun 17, 12:50 UTC45m
2026-06-17 AEZ2629 LIN → OLB Jun 17, 09:15 UTCJun 17, 10:00 UTC45m
2026-06-16 AEZ60RG - Jun 16, 09:50 UTCJun 16, 10:40 UTC50m
2026-06-16 AEZ7117 - Jun 16, 08:00 UTCJun 16, 08:35 UTC35m
2026-06-15 AEZ2363 LIN → CAG Jun 15, 17:50 UTCJun 15, 18:40 UTC50m
2026-06-15 AEZ2362 CAG → LIN Jun 15, 15:55 UTCJun 15, 16:45 UTC50m
2026-06-15 AEZ88LL LIN → CAG Jun 15, 13:45 UTCJun 15, 14:40 UTC55m
2026-06-15 AEZ44LG - Jun 15, 07:10 UTCJun 15, 08:04 UTC55m
2026-06-14 AEZ2364 CAG → LIN Jun 14, 18:00 UTCJun 14, 19:05 UTC1h 5m
2026-06-14 AEZ2360 CAG → LIN Jun 14, 13:35 UTCJun 14, 14:35 UTC1h 0m
2026-06-13 AEZ49KF CAG → LIN Jun 13, 18:25 UTCJun 13, 19:25 UTC1h 0m

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.

Mode-S 4521CF frequently asked

What is Mode-S code 4521CF?
4521CF is an ICAO 24-bit transponder address. Allocated to Bulgaria.
Where is Mode-S 4521CF registered?
Mode-S code 4521CF is allocated to Bulgaria (BG). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4521CF broadcasting right now?
No active broadcast right now. Last signal was 3d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4521CF, octal 21220717, decimal 4,530,639.
What flights does 4521CF operate?
Mode-S 4521CF has broadcast 20 distinct callsigns, including AEZ7810, AEZ70MH, AEZ49KF, AEZ44LG, AEZ2617.