Apparatus

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sensors Mode-S transponder

45CF21

ICAO 24-bit transponder address · allocated to Denmark

Currently assigned to OY-SYA · BOEING 767-300

Hex
45CF21
Octal
21347441
Decimal
4,575,009
Country
DK
Tail
OY-SYA
Type
B763
No current signal · last broadcast 15h ago
Flights observed
81
Distinct callsigns
12
Country
DK
Last broadcast
15h ago

Last known position

Most recent position reported by Mode-S 45CF21.

Country allocation

The ICAO 24-bit address 45CF21 falls within the block assigned to Denmark (DK) by ICAO Annex 10, Volume III. Every aircraft registered in Denmark 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 12 distinct

Callsign Airline Flights Last seen
UPS275 United Parcel Service 25 2026-06-01
UPS274 United Parcel Service 22 2026-06-02
SRR6118 Star Air 13 2026-05-14
SRR6119 Star Air 12 2026-05-12
SRR6498 Star Air 2 2026-05-13
SRR9311 Star Air 1 2026-05-31
SRR9301 - 1 2026-05-30
SRR9211 - 1 2026-04-21
SRR9181 Star Air 1 2026-04-18
SRR7818 - 1 2026-05-12
SRR7119 Star Air 1 2026-05-15
SRR6497 Star Air 1 2026-05-13

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-06-02 UPS274 CGN → BUD Jun 2, 02:15 UTCJun 2, 03:15 UTC1h 0m
2026-06-01 UPS275 VIE → CGN Jun 1, 20:45 UTCJun 1, 22:00 UTC1h 15m
2026-06-01 UPS274 CGN → BUD Jun 1, 00:50 UTCJun 1, 01:50 UTC1h 0m
2026-05-31 SRR9311 CGN → SNN May 31, 16:10 UTCMay 31, 17:35 UTC1h 25m
2026-05-30 SRR9301 - May 30, 05:30 UTCMay 30, 07:05 UTC1h 35m
2026-05-29 UPS275 VIE → CGN May 29, 21:20 UTCMay 29, 22:30 UTC1h 10m
2026-05-29 UPS274 CGN → BUD May 29, 02:15 UTCMay 29, 03:20 UTC1h 5m
2026-05-28 UPS275 VIE → CGN May 28, 20:55 UTCMay 28, 22:10 UTC1h 15m
2026-05-28 UPS274 CGN → BUD May 28, 02:20 UTCMay 28, 03:25 UTC1h 5m
2026-05-27 UPS275 VIE → CGN May 27, 22:20 UTCMay 27, 23:30 UTC1h 10m
2026-05-27 UPS274 CGN → BUD May 27, 02:14 UTCMay 27, 03:14 UTC1h 0m
2026-05-26 UPS275 VIE → CGN May 26, 20:54 UTCMay 26, 22:09 UTC1h 15m
2026-05-26 UPS274 CGN → BUD May 26, 02:15 UTCMay 26, 03:19 UTC1h 5m
2026-05-25 UPS275 VIE → CGN May 25, 20:45 UTCMay 25, 21:49 UTC1h 5m
2026-05-22 UPS275 VIE → CGN May 22, 21:05 UTCMay 22, 22:15 UTC1h 10m
2026-05-22 UPS274 CGN → BUD May 22, 02:15 UTCMay 22, 03:20 UTC1h 5m
2026-05-21 UPS275 VIE → CGN May 21, 20:55 UTCMay 21, 22:20 UTC1h 25m
2026-05-21 UPS274 CGN → BUD May 21, 02:15 UTCMay 21, 03:20 UTC1h 5m
2026-05-20 UPS275 VIE → CGN May 20, 20:45 UTCMay 20, 21:55 UTC1h 10m
2026-05-20 UPS274 CGN → BUD May 20, 02:15 UTCMay 20, 03:20 UTC1h 5m
2026-05-19 UPS275 VIE → CGN May 19, 20:45 UTCMay 19, 21:55 UTC1h 10m
2026-05-19 UPS274 CGN → BUD May 19, 02:10 UTCMay 19, 03:20 UTC1h 10m
2026-05-18 UPS275 VIE → CGN May 18, 20:55 UTCMay 18, 22:00 UTC1h 5m
2026-05-18 UPS274 CGN → BUD May 18, 00:45 UTCMay 18, 01:45 UTC1h 0m
2026-05-15 SRR7119 DUB → MUC May 15, 16:50 UTCMay 15, 19:35 UTC2h 45m
2026-05-14 SRR6118 CGN → ATH May 14, 02:25 UTCMay 14, 04:51 UTC2h 25m
2026-05-13 SRR6497 BLQ → CGN May 13, 20:10 UTCMay 13, 21:20 UTC1h 10m
2026-05-13 SRR6498 CGN → BLQ May 13, 05:15 UTCMay 13, 05:45 UTC30m
2026-05-13 SRR6498 CGN → BLQ May 13, 02:50 UTCMay 13, 03:50 UTC1h 0m
2026-05-12 SRR6119 ATH → CGN May 12, 21:10 UTCMay 12, 21:55 UTC45m
2026-05-12 SRR6119 ATH → CGN May 12, 17:45 UTCMay 12, 20:05 UTC2h 20m
2026-05-12 SRR6118 CGN → ATH May 12, 11:10 UTCMay 12, 13:40 UTC2h 30m
2026-05-12 SRR7818 - May 12, 05:50 UTCMay 12, 06:35 UTC45m
2026-05-12 SRR6118 CGN → ATH May 12, 02:45 UTCMay 12, 03:20 UTC35m
2026-05-11 SRR6119 ATH → CGN May 11, 21:15 UTCMay 11, 21:55 UTC40m
2026-05-11 SRR6119 ATH → CGN May 11, 17:45 UTCMay 11, 20:00 UTC2h 15m
2026-05-11 SRR6118 CGN → ATH May 11, 04:25 UTCMay 11, 06:15 UTC1h 50m
2026-05-11 SRR6118 CGN → ATH May 11, 02:15 UTCMay 11, 03:05 UTC50m
2026-05-06 UPS275 VIE → CGN May 6, 20:45 UTCMay 6, 22:00 UTC1h 15m
2026-05-06 UPS274 CGN → BUD May 6, 02:20 UTCMay 6, 03:25 UTC1h 5m
2026-05-05 UPS275 VIE → CGN May 5, 20:45 UTCMay 5, 21:50 UTC1h 5m
2026-05-05 UPS274 CGN → BUD May 5, 02:01 UTCMay 5, 03:10 UTC1h 10m
2026-05-04 UPS275 VIE → CGN May 4, 20:45 UTCMay 4, 22:00 UTC1h 15m
2026-05-04 UPS274 CGN → BUD May 4, 00:45 UTCMay 4, 01:50 UTC1h 5m
2026-04-30 SRR6119 ATH → CGN Apr 30, 21:15 UTCApr 30, 22:00 UTC45m
2026-04-30 SRR6119 ATH → CGN Apr 30, 17:35 UTCApr 30, 19:50 UTC2h 15m
2026-04-30 SRR6118 CGN → ATH Apr 30, 04:40 UTCApr 30, 06:35 UTC1h 55m
2026-04-30 SRR6118 CGN → ATH Apr 30, 02:30 UTCApr 30, 03:15 UTC45m
2026-04-29 SRR6119 ATH → CGN Apr 29, 21:20 UTCApr 29, 22:40 UTC1h 20m
2026-04-29 SRR6119 ATH → CGN Apr 29, 17:55 UTCApr 29, 20:10 UTC2h 15m

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 OY-SYA page for operator, model, and routing details .

Mode-S 45CF21 frequently asked

What is Mode-S code 45CF21?
45CF21 is an ICAO 24-bit transponder address. Allocated to Denmark. Assigned to OY-SYA.
Where is Mode-S 45CF21 registered?
Mode-S code 45CF21 is allocated to Denmark (DK). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 45CF21 broadcasting right now?
No active broadcast right now. Last signal was 15h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 45CF21, octal 21347441, decimal 4,575,009.
What flights does 45CF21 operate?
Mode-S 45CF21 has broadcast 12 distinct callsigns, including UPS275, UPS274, SRR6118, SRR6119, SRR6498.