Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

4521B2

ICAO 24-bit transponder address · allocated to Bulgaria

Hex
4521B2
Octal
21220662
Decimal
4,530,610
Country
BG
No current signal · last broadcast 23d ago
Flights observed
90
Distinct callsigns
20
Country
BG
Last broadcast
23d ago

Last known position

Most recent position reported by Mode-S 4521B2.

Country allocation

The ICAO 24-bit address 4521B2 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
GPX701 GP Aviation 8 2026-07-25
GPX700 GP Aviation 8 2026-07-25
GPX807 GP Aviation 5 2026-07-24
GPX806 GP Aviation 5 2026-07-24
GPX7EJ - 5 2026-07-22
GPX2MI GP Aviation 5 2026-07-23
GPX2IM GP Aviation 5 2026-07-23
GPX7JE - 4 2026-07-20
GPX601 GP Aviation 4 2026-07-26
GPX600 GP Aviation 4 2026-07-26
GPX809 GP Aviation 3 2026-07-24
GPX808 GP Aviation 3 2026-07-24
GPX7113 GP Aviation 3 2026-07-19
GPX7112 - 3 2026-07-19
GPX802 GP Aviation 2 2026-07-18
GPX7961 GP Aviation 2 2026-07-26
GPX7960 GP Aviation 2 2026-07-25
GPX605 - 2 2026-07-17
GPX604 - 2 2026-07-17
GPX4961 GP Aviation 2 2026-07-23

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 GPX601 ZRH → PRN Jul 26, 19:20 UTCJul 26, 20:30 UTC1h 10m
2026-07-26 GPX600 PRN → ZRH Jul 26, 12:55 UTCJul 26, 18:00 UTC5h 5m
2026-07-26 GPX1BL PRN → BSL Jul 26, 10:30 UTCJul 26, 11:50 UTC1h 20m
2026-07-26 GPX7961 HEL → PRN Jul 26, 05:25 UTCJul 26, 08:10 UTC2h 46m
2026-07-25 GPX7960 PRN → HEL Jul 25, 19:30 UTCJul 26, 03:55 UTC8h 25m
2026-07-25 GPX701 GVA → PRN Jul 25, 12:30 UTCJul 25, 17:30 UTC5h 0m
2026-07-25 GPX700 PRN → GVA Jul 25, 06:10 UTCJul 25, 11:05 UTC4h 55m
2026-07-24 GPX807 BSL → PRN Jul 24, 19:55 UTCJul 25, 05:00 UTC9h 5m
2026-07-24 GPX806 PRN → BSL Jul 24, 17:00 UTCJul 24, 18:50 UTC1h 50m
2026-07-24 GPX809 BSL → PRN Jul 24, 13:35 UTCJul 24, 15:10 UTC1h 35m
2026-07-24 GPX808 PRN → BSL Jul 24, 10:35 UTCJul 24, 12:20 UTC1h 45m
2026-07-23 GPX2IM BSL → PRN Jul 23, 19:05 UTCJul 23, 20:30 UTC1h 25m
2026-07-23 GPX2MI PRN → BSL Jul 23, 16:00 UTCJul 23, 17:40 UTC1h 40m
2026-07-23 GPX4961 HEL → PRN Jul 23, 10:45 UTCJul 23, 13:40 UTC2h 55m
2026-07-23 GPX4960 PRN → HEL Jul 23, 06:20 UTCJul 23, 09:05 UTC2h 45m
2026-07-22 GPX3281 BER → PRN Jul 22, 18:40 UTCJul 22, 20:15 UTC1h 35m
2026-07-22 GPX3280 PRN → BER Jul 22, 15:10 UTCJul 22, 16:55 UTC1h 45m
2026-07-22 GPX7EJ - Jul 22, 11:10 UTCJul 22, 13:00 UTC1h 50m
2026-07-21 GPX9RE - Jul 21, 20:30 UTCJul 21, 22:25 UTC1h 55m
2026-07-21 GPX9ER - Jul 21, 16:25 UTCJul 21, 19:25 UTC3h 0m
2026-07-21 GPX701 GVA → PRN Jul 21, 12:45 UTCJul 21, 14:20 UTC1h 35m
2026-07-21 GPX700 PRN → GVA Jul 21, 09:05 UTCJul 21, 11:15 UTC2h 10m
2026-07-20 GPX7EJ - Jul 20, 19:00 UTCJul 20, 21:25 UTC2h 25m
2026-07-20 GPX7JE - Jul 20, 15:10 UTCJul 20, 17:45 UTC2h 35m
2026-07-19 GPX807 BSL → PRN Jul 19, 18:05 UTCJul 19, 19:40 UTC1h 35m
2026-07-19 GPX7113 OHD → BSL Jul 19, 15:00 UTCJul 19, 16:55 UTC1h 55m
2026-07-19 GPX7112 - Jul 19, 12:20 UTCJul 19, 13:50 UTC1h 30m
2026-07-19 GPX806 PRN → BSL Jul 19, 09:20 UTCJul 19, 11:05 UTC1h 45m
2026-07-18 GPX2IM - Jul 18, 18:45 UTCJul 18, 20:15 UTC1h 30m
2026-07-18 GPX2MI - Jul 18, 15:45 UTCJul 18, 17:35 UTC1h 50m
2026-07-18 GPX701 - Jul 18, 12:15 UTCJul 18, 13:50 UTC1h 35m
2026-07-18 GPX700 - Jul 18, 06:20 UTCJul 18, 11:00 UTC4h 40m
2026-07-18 GPX802 PRN → BSL Jul 18, 03:15 UTCJul 18, 05:00 UTC1h 45m
2026-07-17 GPX601 - Jul 17, 20:35 UTCJul 17, 22:00 UTC1h 25m
2026-07-17 GPX600 - Jul 17, 17:09 UTCJul 17, 19:15 UTC2h 5m
2026-07-17 GPX809 BSL → PRN Jul 17, 14:10 UTCJul 17, 15:49 UTC1h 40m
2026-07-17 GPX808 PRN → BSL Jul 17, 10:40 UTCJul 17, 13:00 UTC2h 20m
2026-07-17 GPX605 - Jul 17, 06:40 UTCJul 17, 08:00 UTC1h 20m
2026-07-17 GPX604 - Jul 17, 02:50 UTCJul 17, 04:39 UTC1h 50m
2026-07-16 GPX2IM - Jul 16, 18:50 UTCJul 16, 20:19 UTC1h 30m
2026-07-16 GPX2MI - Jul 16, 15:25 UTCJul 16, 17:30 UTC2h 5m
2026-07-16 GPX4961 - Jul 16, 10:40 UTCJul 16, 13:20 UTC2h 40m
2026-07-16 GPX4960 - Jul 16, 06:10 UTCJul 16, 09:00 UTC2h 50m
2026-07-15 GPX3281 - Jul 15, 18:45 UTCJul 15, 20:15 UTC1h 30m
2026-07-15 GPX3280 - Jul 15, 15:10 UTCJul 15, 17:05 UTC1h 55m
2026-07-15 GPX7EJ - Jul 15, 11:05 UTCJul 15, 13:35 UTC2h 30m
2026-07-15 GPX7JE - Jul 15, 06:20 UTCJul 15, 08:55 UTC2h 35m
2026-07-14 GPX701 - Jul 14, 12:20 UTCJul 14, 13:50 UTC1h 30m
2026-07-14 GPX700 - Jul 14, 09:05 UTCJul 14, 11:00 UTC1h 55m
2026-07-13 GPX7EJ - Jul 13, 19:00 UTCJul 13, 21:25 UTC2h 25m

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 4521B2 frequently asked

What is Mode-S code 4521B2?
4521B2 is an ICAO 24-bit transponder address. Allocated to Bulgaria.
Where is Mode-S 4521B2 registered?
Mode-S code 4521B2 is allocated to Bulgaria (BG). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4521B2 broadcasting right now?
No active broadcast right now. Last signal was 23d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4521B2, octal 21220662, decimal 4,530,610.
What flights does 4521B2 operate?
Mode-S 4521B2 has broadcast 20 distinct callsigns, including GPX701, GPX700, GPX807, GPX806, GPX7EJ.