Apparatus

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sensors Mode-S transponder

501DD1

ICAO 24-bit transponder address · allocated to Croatia

Currently assigned to 9A-CQF · DE HAVILLAND DHC-8-400 Dash 8

Hex
501DD1
Octal
24016721
Decimal
5,250,513
Country
HR
Tail
9A-CQF
Type
DH8D
No current signal · last broadcast 5h ago
Flights observed
352
Distinct callsigns
20
Country
HR
Last broadcast
5h ago

Last known position

Most recent position reported by Mode-S 501DD1.

Country allocation

The ICAO 24-bit address 501DD1 falls within the block assigned to Croatia (HR) by ICAO Annex 10, Volume III. Every aircraft registered in Croatia 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
CTN632 - 23 2026-05-27
CTN3T Croatia Airlines 20 2026-05-28
CTN443 Croatia Airlines 16 2026-05-29
CTN4AT Croatia Airlines 15 2026-05-29
CTN442 Croatia Airlines 15 2026-05-29
CTN441 Croatia Airlines 15 2026-05-29
CTN342 Croatia Airlines 15 2026-05-29
CTN341 Croatia Airlines 14 2026-05-24
CTN4W Croatia Airlines 13 2026-05-25
CTN344 Croatia Airlines 13 2026-05-28
CTN6CH Croatia Airlines 12 2026-05-24
CTN465 Croatia Airlines 11 2026-05-24
CTN461 Croatia Airlines 11 2026-05-24
CTN345 Croatia Airlines 11 2026-05-28
CTN460 Croatia Airlines 10 2026-05-24
CTN4437 Croatia Airlines 8 2026-05-27
CTN436R Croatia Airlines 8 2026-05-27
CTN7T Croatia Airlines 7 2026-05-03
CTN6H Croatia Airlines 7 2026-05-28
CTN4Z Croatia Airlines 6 2026-05-25

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-29 CTN342 ZAG → SJJ May 29, 20:05 UTCMay 29, 20:35 UTC30m
2026-05-29 CTN443 VIE → ZAG May 29, 18:00 UTCMay 29, 18:30 UTC30m
2026-05-29 CTN442 ZAG → VIE May 29, 16:20 UTCMay 29, 16:50 UTC30m
2026-05-29 CTN2S ZAG → SPU May 29, 09:55 UTCMay 29, 10:15 UTC20m
2026-05-29 CTN441 VIE → ZAG May 29, 08:05 UTCMay 29, 08:35 UTC30m
2026-05-29 CTN4AT ZAG → VIE May 29, 06:05 UTCMay 29, 06:40 UTC35m
2026-05-29 CTN78M SKP → ZAG May 29, 03:40 UTCMay 29, 04:40 UTC1h 0m
2026-05-28 CTN366 ZAG → SKP May 28, 20:10 UTCMay 28, 21:05 UTC55m
2026-05-28 CTN443 VIE → ZAG May 28, 17:50 UTCMay 28, 18:25 UTC35m
2026-05-28 CTN442 ZAG → VIE May 28, 16:10 UTCMay 28, 16:45 UTC35m
2026-05-28 CTN345 SJJ → ZAG May 28, 14:25 UTCMay 28, 14:55 UTC30m
2026-05-28 CTN344 ZAG → SJJ May 28, 13:20 UTCMay 28, 13:45 UTC25m
2026-05-28 CTN6H ZAG → SJJ May 28, 11:30 UTCMay 28, 12:20 UTC50m
2026-05-28 CTN8Y ZAG → DBV May 28, 09:55 UTCMay 28, 10:35 UTC40m
2026-05-28 CTN441 VIE → ZAG May 28, 08:00 UTCMay 28, 08:35 UTC35m
2026-05-28 CTN4AT ZAG → VIE May 28, 06:15 UTCMay 28, 06:45 UTC30m
2026-05-28 CTN3T PUY → ZAG May 28, 04:55 UTCMay 28, 05:15 UTC20m
2026-05-28 CTN3T PUY → ZAG May 28, 04:05 UTCMay 28, 04:25 UTC20m
2026-05-27 CTN632 - May 27, 20:50 UTCMay 27, 21:10 UTC20m
2026-05-27 CTN632 - May 27, 19:40 UTCMay 27, 20:15 UTC35m
2026-05-27 CTN443 VIE → ZAG May 27, 17:50 UTCMay 27, 18:20 UTC30m
2026-05-27 CTN442 ZAG → VIE May 27, 16:10 UTCMay 27, 16:45 UTC35m
2026-05-27 CTN321 - May 27, 12:30 UTCMay 27, 13:30 UTC1h 0m
2026-05-27 CTN320 ZAG → PRG May 27, 10:35 UTCMay 27, 11:30 UTC55m
2026-05-27 CTN4437 MUC → ZAG May 27, 08:35 UTCMay 27, 09:25 UTC50m
2026-05-27 CTN436R ZAG → MUC May 27, 06:15 UTCMay 27, 07:10 UTC55m
2026-05-27 CTN3T PUY → ZAG May 27, 04:55 UTCMay 27, 05:09 UTC15m
2026-05-27 CTN3T PUY → ZAG May 27, 04:04 UTCMay 27, 04:24 UTC20m
2026-05-26 CTN632 - May 26, 20:50 UTCMay 26, 21:09 UTC20m
2026-05-26 CTN632 - May 26, 19:45 UTCMay 26, 20:09 UTC25m
2026-05-26 CTN443 VIE → ZAG May 26, 17:50 UTCMay 26, 18:24 UTC35m
2026-05-26 CTN442 ZAG → VIE May 26, 16:10 UTCMay 26, 16:45 UTC35m
2026-05-26 CTN345 SJJ → ZAG May 26, 14:30 UTCMay 26, 15:00 UTC30m
2026-05-26 CTN344 ZAG → SJJ May 26, 13:10 UTCMay 26, 13:40 UTC30m
2026-05-26 CTN6X DBV → ZAG May 26, 11:20 UTCMay 26, 12:05 UTC45m
2026-05-26 CTN660 ZAG → DBV May 26, 09:45 UTCMay 26, 10:25 UTC40m
2026-05-26 CTN441 VIE → ZAG May 26, 07:59 UTCMay 26, 08:34 UTC35m
2026-05-26 CTN4AT ZAG → VIE May 26, 06:20 UTCMay 26, 06:54 UTC35m
2026-05-26 CTN3T PUY → ZAG May 26, 05:05 UTCMay 26, 05:25 UTC20m
2026-05-26 CTN3T PUY → ZAG May 26, 04:10 UTCMay 26, 04:30 UTC20m
2026-05-25 CTN632 - May 25, 20:30 UTCMay 25, 20:50 UTC20m
2026-05-25 CTN632 - May 25, 19:35 UTCMay 25, 19:59 UTC25m
2026-05-25 CTN443 VIE → ZAG May 25, 17:55 UTCMay 25, 18:30 UTC35m
2026-05-25 CTN442 ZAG → VIE May 25, 16:05 UTCMay 25, 16:40 UTC35m
2026-05-25 CTN4Z PUY → ZAG May 25, 14:30 UTCMay 25, 14:50 UTC20m
2026-05-25 CTN4W ZAG → ZAD May 25, 13:25 UTCMay 25, 13:45 UTC20m
2026-05-25 CTN4W ZAG → ZAD May 25, 12:20 UTCMay 25, 12:45 UTC25m
2026-05-25 CTN4437 MUC → ZAG May 25, 08:35 UTCMay 25, 09:20 UTC45m
2026-05-25 CTN436R ZAG → MUC May 25, 06:25 UTCMay 25, 07:20 UTC55m
2026-05-25 CTN6B DBV → ZAG May 25, 04:10 UTCMay 25, 04:55 UTC45m

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 9A-CQF page for operator, model, and routing details .

Mode-S 501DD1 frequently asked

What is Mode-S code 501DD1?
501DD1 is an ICAO 24-bit transponder address. Allocated to Croatia. Assigned to 9A-CQF.
Where is Mode-S 501DD1 registered?
Mode-S code 501DD1 is allocated to Croatia (HR). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 501DD1 broadcasting right now?
No active broadcast right now. Last signal was 5h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 501DD1, octal 24016721, decimal 5,250,513.
What flights does 501DD1 operate?
Mode-S 501DD1 has broadcast 20 distinct callsigns, including CTN632, CTN3T, CTN443, CTN4AT, CTN442.