Apparatus

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sensors Mode-S transponder

4521BB

ICAO 24-bit transponder address · allocated to Bulgaria

Hex
4521BB
Octal
21220673
Decimal
4,530,619
Country
BG
No current signal · last broadcast 15d ago
Flights observed
136
Distinct callsigns
20
Country
BG
Last broadcast
15d ago

Last known position

Most recent position reported by Mode-S 4521BB.

Country allocation

The ICAO 24-bit address 4521BB 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
EAF6082 European Aviation Air Charter 10 2026-07-26
EAF6081 - 9 2026-07-26
EAF772 - 5 2026-07-26
EAF771 - 5 2026-07-26
EAF576 - 5 2026-07-24
EAF575 - 5 2026-07-24
EAF574 - 5 2026-07-24
EAF573 - 5 2026-07-24
EAF2077 - 5 2026-07-25
EAF2076 European Aviation Air Charter 5 2026-07-25
EAF701 - 4 2026-07-26
EAF602 European Aviation Air Charter 4 2026-07-26
EAF601 - 4 2026-07-25
EAF402 European Aviation Air Charter 4 2026-07-24
EAF401 - 4 2026-07-23
EAF302 European Aviation Air Charter 4 2026-07-23
EAF301 - 4 2026-07-22
EAF252 - 4 2026-07-21
EAF251 - 4 2026-07-21
EAF176 European Aviation Air Charter 4 2026-07-20

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 EAF701 - Jul 26, 21:40 UTCJul 26, 22:45 UTC1h 5m
2026-07-26 EAF772 - Jul 26, 18:40 UTCJul 26, 19:50 UTC1h 10m
2026-07-26 EAF771 - Jul 26, 15:20 UTCJul 26, 16:35 UTC1h 15m
2026-07-26 EAF6082 TLV → VAR Jul 26, 12:20 UTCJul 26, 14:10 UTC1h 50m
2026-07-26 EAF6081 - Jul 26, 08:50 UTCJul 26, 10:40 UTC1h 50m
2026-07-26 EAF602 TLV → BOJ Jul 26, 01:50 UTCJul 26, 03:40 UTC1h 50m
2026-07-25 EAF601 - Jul 25, 22:10 UTCJul 25, 23:55 UTC1h 45m
2026-07-25 EAF2077 LEJ → BOJ Jul 25, 08:35 UTCJul 25, 10:45 UTC2h 10m
2026-07-25 EAF2076 BOJ → LEJ Jul 25, 05:00 UTCJul 25, 07:10 UTC2h 10m
2026-07-24 EAF574 - Jul 24, 18:15 UTCJul 24, 19:50 UTC1h 35m
2026-07-24 EAF575 - Jul 24, 15:10 UTCJul 24, 17:00 UTC1h 50m
2026-07-24 EAF576 - Jul 24, 12:30 UTCJul 24, 13:55 UTC1h 25m
2026-07-24 EAF573 - Jul 24, 09:35 UTCJul 24, 11:10 UTC1h 35m
2026-07-24 EAF402 FCO → VAR Jul 24, 02:40 UTCJul 24, 04:25 UTC1h 45m
2026-07-23 EAF401 - Jul 23, 23:10 UTCJul 24, 00:55 UTC1h 45m
2026-07-23 EAF6082 TLV → VAR Jul 23, 10:55 UTCJul 23, 12:50 UTC1h 55m
2026-07-23 EAF6081 - Jul 23, 07:40 UTCJul 23, 09:25 UTC1h 45m
2026-07-23 EAF302 TLV → BOJ Jul 23, 03:05 UTCJul 23, 04:55 UTC1h 50m
2026-07-22 EAF301 - Jul 22, 22:05 UTCJul 22, 23:55 UTC1h 50m
2026-07-22 EAF6082 - Jul 22, 11:35 UTCJul 22, 13:30 UTC1h 55m
2026-07-22 EAF202 TLV → BOJ Jul 22, 02:05 UTCJul 22, 04:00 UTC1h 55m
2026-07-21 EAF201 VAR → OSR Jul 21, 22:05 UTCJul 21, 23:55 UTC1h 50m
2026-07-21 EAF252 - Jul 21, 07:20 UTCJul 21, 08:35 UTC1h 15m
2026-07-21 EAF251 - Jul 21, 04:35 UTCJul 21, 06:05 UTC1h 30m
2026-07-20 EAF176 BRQ → BOJ Jul 20, 16:55 UTCJul 20, 18:05 UTC1h 10m
2026-07-20 EAF175 - Jul 20, 14:55 UTCJul 20, 16:00 UTC1h 5m
2026-07-20 EAF102 - Jul 20, 11:05 UTCJul 20, 13:00 UTC1h 55m
2026-07-20 EAF101 - Jul 20, 07:50 UTCJul 20, 09:40 UTC1h 50m
2026-07-20 EAF702 TLV → BOJ Jul 20, 02:25 UTCJul 20, 04:10 UTC1h 45m
2026-07-19 EAF701 - Jul 19, 21:55 UTCJul 19, 23:40 UTC1h 45m
2026-07-19 EAF772 - Jul 19, 18:05 UTCJul 19, 19:20 UTC1h 15m
2026-07-19 EAF771 - Jul 19, 15:35 UTCJul 19, 16:50 UTC1h 15m
2026-07-19 EAF6082 - Jul 19, 12:20 UTCJul 19, 14:10 UTC1h 50m
2026-07-19 EAF6081 - Jul 19, 09:05 UTCJul 19, 11:00 UTC1h 55m
2026-07-19 EAF602 TLV → BOJ Jul 19, 05:30 UTCJul 19, 07:15 UTC1h 45m
2026-07-19 EAF601 - Jul 19, 01:10 UTCJul 19, 02:55 UTC1h 45m
2026-07-18 EAF602P OSR → VAR Jul 18, 22:15 UTCJul 18, 23:35 UTC1h 20m
2026-07-18 EAF9641 - Jul 18, 14:05 UTCJul 18, 21:15 UTC7h 10m
2026-07-18 EAF603P PMI → STN Jul 18, 11:15 UTCJul 18, 12:50 UTC1h 35m
2026-07-18 EAF2077 LEJ → BOJ Jul 18, 08:35 UTCJul 18, 10:25 UTC1h 50m
2026-07-18 EAF2076 BOJ → LEJ Jul 18, 05:20 UTCJul 18, 07:25 UTC2h 5m
2026-07-17 EAF574 - Jul 17, 18:44 UTCJul 17, 20:25 UTC1h 40m
2026-07-17 EAF575 - Jul 17, 15:55 UTCJul 17, 17:44 UTC1h 50m
2026-07-17 EAF576 - Jul 17, 12:40 UTCJul 17, 14:04 UTC1h 25m
2026-07-17 EAF573 - Jul 17, 10:00 UTCJul 17, 11:35 UTC1h 35m
2026-07-17 EAF402 FCO → VAR Jul 17, 02:54 UTCJul 17, 04:44 UTC1h 50m
2026-07-16 EAF401 - Jul 16, 23:35 UTCJul 17, 01:15 UTC1h 40m
2026-07-16 EAF6082 - Jul 16, 10:45 UTCJul 16, 12:34 UTC1h 50m
2026-07-16 EAF6081 - Jul 16, 07:30 UTCJul 16, 09:20 UTC1h 50m
2026-07-16 EAF302 - Jul 16, 02:20 UTCJul 16, 04:00 UTC1h 40m

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 4521BB frequently asked

What is Mode-S code 4521BB?
4521BB is an ICAO 24-bit transponder address. Allocated to Bulgaria.
Where is Mode-S 4521BB registered?
Mode-S code 4521BB is allocated to Bulgaria (BG). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4521BB broadcasting right now?
No active broadcast right now. Last signal was 15d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4521BB, octal 21220673, decimal 4,530,619.
What flights does 4521BB operate?
Mode-S 4521BB has broadcast 20 distinct callsigns, including EAF6082, EAF6081, EAF772, EAF771, EAF576.