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 4h ago
Flights observed
156
Distinct callsigns
18
Country
DK
Last broadcast
4h 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 18 distinct

Callsign Airline Flights Last seen
UPS275 - 55 2026-07-16
UPS274 - 51 2026-07-16
SRR6118 Star Air 13 2026-05-14
SRR6119 Star Air 12 2026-05-12
UPS292 - 4 2026-06-25
UPS291 - 4 2026-06-25
SRR6402 Star Air 4 2026-07-17
SRR6498 Star Air 2 2026-05-13
SRR6401 - 2 2026-07-17
SRR9311 Star Air 1 2026-05-31
SRR9301 - 1 2026-05-30
SRR9211 - 1 2026-04-21
SRR9181 Star Air 1 2026-04-18
SRR9071 Star Air 1 2026-06-07
SRR9051 Star Air 1 2026-06-05
SRR7818 - 1 2026-05-12
SRR7119 Star Air 1 2026-05-15
SRR6497 Star Air 1 2026-05-13

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-17 SRR6401 - Jul 17, 21:00 UTCJul 17, 22:00 UTC1h 0m
2026-07-17 SRR6401 - Jul 17, 18:25 UTCJul 17, 19:00 UTC35m
2026-07-17 SRR6402 CGN → AOI Jul 17, 05:45 UTCJul 17, 06:25 UTC40m
2026-07-17 SRR6402 CGN → AOI Jul 17, 01:00 UTCJul 17, 02:05 UTC1h 5m
2026-07-16 UPS275 - Jul 16, 21:00 UTCJul 16, 22:10 UTC1h 10m
2026-07-16 UPS274 - Jul 16, 02:15 UTCJul 16, 03:15 UTC1h 0m
2026-07-15 UPS275 - Jul 15, 20:55 UTCJul 15, 22:25 UTC1h 30m
2026-07-15 UPS274 - Jul 15, 02:15 UTCJul 15, 03:15 UTC1h 0m
2026-07-14 UPS275 - Jul 14, 20:55 UTCJul 14, 22:05 UTC1h 10m
2026-07-14 UPS274 - Jul 14, 02:15 UTCJul 14, 03:15 UTC1h 0m
2026-07-13 UPS275 - Jul 13, 20:55 UTCJul 13, 22:15 UTC1h 20m
2026-07-13 UPS274 - Jul 13, 00:45 UTCJul 13, 01:45 UTC1h 0m
2026-07-10 UPS275 - Jul 10, 20:50 UTCJul 10, 22:00 UTC1h 10m
2026-07-10 UPS274 - Jul 10, 02:15 UTCJul 10, 03:15 UTC1h 0m
2026-07-09 UPS275 - Jul 9, 20:50 UTCJul 9, 21:55 UTC1h 5m
2026-07-09 UPS274 CGN → VIE Jul 9, 02:20 UTCJul 9, 03:25 UTC1h 5m
2026-07-08 UPS275 VIE → CGN Jul 8, 20:55 UTCJul 8, 22:15 UTC1h 20m
2026-07-08 UPS274 CGN → VIE Jul 8, 02:25 UTCJul 8, 03:25 UTC1h 0m
2026-07-07 UPS275 - Jul 7, 20:50 UTCJul 7, 22:10 UTC1h 20m
2026-07-07 UPS274 - Jul 7, 02:15 UTCJul 7, 03:15 UTC1h 0m
2026-07-06 UPS275 VIE → CGN Jul 6, 20:55 UTCJul 6, 22:10 UTC1h 15m
2026-07-06 UPS274 CGN → VIE Jul 6, 00:55 UTCJul 6, 01:55 UTC1h 0m
2026-07-03 UPS275 - Jul 3, 20:45 UTCJul 3, 22:05 UTC1h 20m
2026-07-03 UPS274 - Jul 3, 02:20 UTCJul 3, 03:20 UTC1h 0m
2026-07-02 UPS275 - Jul 2, 20:55 UTCJul 2, 22:05 UTC1h 10m
2026-07-02 UPS274 - Jul 2, 02:20 UTCJul 2, 03:25 UTC1h 5m
2026-07-01 UPS275 - Jul 1, 20:50 UTCJul 1, 22:00 UTC1h 10m
2026-07-01 UPS274 - Jul 1, 02:30 UTCJul 1, 03:35 UTC1h 5m
2026-06-30 UPS275 - Jun 30, 20:50 UTCJun 30, 22:00 UTC1h 10m
2026-06-30 UPS274 - Jun 30, 02:25 UTCJun 30, 03:30 UTC1h 5m
2026-06-29 UPS275 - Jun 29, 20:59 UTCJun 29, 22:15 UTC1h 15m
2026-06-29 UPS274 - Jun 29, 00:54 UTCJun 29, 01:55 UTC1h 0m
2026-06-26 UPS275 VIE → CGN Jun 26, 20:50 UTCJun 26, 21:59 UTC1h 10m
2026-06-26 UPS274 - Jun 26, 02:14 UTCJun 26, 03:20 UTC1h 5m
2026-06-25 UPS291 - Jun 25, 21:44 UTCJun 25, 22:59 UTC1h 15m
2026-06-25 UPS291 - Jun 25, 19:29 UTCJun 25, 20:45 UTC1h 15m
2026-06-25 UPS292 - Jun 25, 03:50 UTCJun 25, 05:09 UTC1h 20m
2026-06-25 UPS292 CGN → MMX Jun 25, 01:54 UTCJun 25, 02:54 UTC1h 0m
2026-06-24 UPS275 - Jun 24, 20:49 UTCJun 24, 21:54 UTC1h 5m
2026-06-24 UPS274 - Jun 24, 02:15 UTCJun 24, 03:19 UTC1h 5m
2026-06-23 UPS275 VIE → CGN Jun 23, 20:49 UTCJun 23, 22:05 UTC1h 15m
2026-06-23 UPS274 CGN → VIE Jun 23, 02:15 UTCJun 23, 03:20 UTC1h 5m
2026-06-22 UPS275 - Jun 22, 20:55 UTCJun 22, 22:10 UTC1h 15m
2026-06-22 UPS274 - Jun 22, 00:55 UTCJun 22, 01:55 UTC1h 0m
2026-06-19 UPS275 - Jun 19, 20:55 UTCJun 19, 22:19 UTC1h 25m
2026-06-19 UPS274 - Jun 19, 02:19 UTCJun 19, 03:24 UTC1h 5m
2026-06-18 UPS275 - Jun 18, 20:55 UTCJun 18, 22:30 UTC1h 35m
2026-06-18 UPS274 - Jun 18, 02:10 UTCJun 18, 03:10 UTC1h 0m
2026-06-17 UPS275 VIE → CGN Jun 17, 21:00 UTCJun 17, 22:25 UTC1h 25m
2026-06-17 UPS274 CGN → VIE Jun 17, 02:30 UTCJun 17, 03:30 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.

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 4h 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 18 distinct callsigns, including UPS275, UPS274, SRR6118, SRR6119, UPS292.