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sensors Mode-S transponder

4021CF

ICAO 24-bit transponder address · allocated to United Kingdom

Currently assigned to G-FULL · PIPER PA-28R-180/200/201

Hex
4021CF
Octal
20020717
Decimal
4,202,959
Country
GB
Tail
G-FULL
Type
P28R
No current signal · last broadcast 13h ago
Flights observed
93
Distinct callsigns
6
Country
GB
Last broadcast
13h ago

Last known position

Most recent position reported by Mode-S 4021CF.

Country allocation

The ICAO 24-bit address 4021CF falls within the block assigned to United Kingdom (GB) by ICAO Annex 10, Volume III. Every aircraft registered in United Kingdom 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 6 distinct

Callsign Airline Flights Last seen
STL29 - 36 2026-07-17
STL36 - 31 2026-07-16
STL02 - 22 2026-07-17
GBNUT - 2 2026-04-18
STL18 - 1 2026-04-16
GFULL - 1 2026-04-15

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-17 STL02 - Jul 17, 14:50 UTCJul 17, 15:40 UTC50m
2026-07-17 STL29 - Jul 17, 09:20 UTCJul 17, 10:35 UTC1h 15m
2026-07-16 STL36 - Jul 16, 14:45 UTCJul 16, 15:45 UTC1h 0m
2026-07-15 STL36 - Jul 15, 16:15 UTCJul 15, 17:10 UTC55m
2026-07-15 STL02 - Jul 15, 13:35 UTCJul 15, 15:00 UTC1h 25m
2026-07-14 STL36 - Jul 14, 14:10 UTCJul 14, 15:05 UTC55m
2026-07-14 STL02 - Jul 14, 10:40 UTCJul 14, 11:20 UTC40m
2026-07-14 STL29 - Jul 14, 07:30 UTCJul 14, 08:30 UTC1h 0m
2026-07-13 STL36 - Jul 13, 16:00 UTCJul 13, 16:45 UTC45m
2026-07-10 STL29 - Jul 10, 10:15 UTCJul 10, 11:25 UTC1h 10m
2026-07-10 STL29 - Jul 10, 07:00 UTCJul 10, 07:55 UTC55m
2026-07-07 STL36 - Jul 7, 13:55 UTCJul 7, 14:45 UTC50m
2026-07-07 STL29 - Jul 7, 11:20 UTCJul 7, 12:15 UTC55m
2026-07-07 STL29 - Jul 7, 09:35 UTCJul 7, 10:30 UTC55m
2026-07-07 STL29 - Jul 7, 07:20 UTCJul 7, 08:15 UTC55m
2026-07-06 STL36 - Jul 6, 15:50 UTCJul 6, 16:55 UTC1h 5m
2026-07-06 STL29 - Jul 6, 08:10 UTCJul 6, 09:20 UTC1h 10m
2026-07-05 STL29 - Jul 5, 09:40 UTCJul 5, 10:40 UTC1h 0m
2026-07-05 STL29 - Jul 5, 07:20 UTCJul 5, 09:00 UTC1h 40m
2026-07-03 STL02 - Jul 3, 14:25 UTCJul 3, 16:00 UTC1h 35m
2026-07-03 STL29 - Jul 3, 11:15 UTCJul 3, 11:55 UTC40m
2026-07-01 STL29 - Jul 1, 13:10 UTCJul 1, 14:00 UTC50m
2026-07-01 STL36 - Jul 1, 10:10 UTCJul 1, 12:20 UTC2h 10m
2026-06-30 STL29 - Jun 30, 13:20 UTCJun 30, 14:25 UTC1h 5m
2026-06-30 STL02 - Jun 30, 12:00 UTCJun 30, 12:45 UTC45m
2026-06-30 STL02 - Jun 30, 09:55 UTCJun 30, 10:55 UTC1h 0m
2026-06-29 STL36 - Jun 29, 16:04 UTCJun 29, 16:55 UTC50m
2026-06-29 STL36 - Jun 29, 13:59 UTCJun 29, 14:50 UTC50m
2026-06-25 STL36 - Jun 25, 16:29 UTCJun 25, 17:09 UTC40m
2026-06-25 STL36 - Jun 25, 11:59 UTCJun 25, 12:54 UTC55m
2026-06-24 STL36 - Jun 24, 15:59 UTCJun 24, 16:45 UTC45m
2026-06-24 STL02 - Jun 24, 09:59 UTCJun 24, 10:55 UTC55m
2026-06-23 STL36 - Jun 23, 13:29 UTCJun 23, 14:29 UTC1h 0m
2026-06-23 STL29 - Jun 23, 11:24 UTCJun 23, 12:20 UTC55m
2026-06-22 STL36 - Jun 22, 16:24 UTCJun 22, 17:20 UTC55m
2026-06-22 STL29 - Jun 22, 07:30 UTCJun 22, 08:15 UTC45m
2026-06-20 STL36 - Jun 20, 16:44 UTCJun 20, 17:34 UTC50m
2026-06-19 STL36 - Jun 19, 16:14 UTCJun 19, 17:19 UTC1h 5m
2026-06-19 STL36 - Jun 19, 13:44 UTCJun 19, 14:54 UTC1h 10m
2026-06-19 STL29 - Jun 19, 10:14 UTCJun 19, 11:24 UTC1h 10m
2026-06-19 STL29 - Jun 19, 07:34 UTCJun 19, 08:44 UTC1h 10m
2026-06-18 STL36 - Jun 18, 13:10 UTCJun 18, 14:05 UTC55m
2026-06-18 STL36 - Jun 18, 07:55 UTCJun 18, 08:40 UTC45m
2026-06-17 STL36 - Jun 17, 16:20 UTCJun 17, 17:15 UTC55m
2026-06-15 STL36 - Jun 15, 15:00 UTCJun 15, 15:40 UTC40m
2026-06-15 STL29 - Jun 15, 09:45 UTCJun 15, 11:05 UTC1h 20m
2026-06-14 STL36 - Jun 14, 12:30 UTCJun 14, 13:30 UTC1h 0m
2026-06-14 STL29 - Jun 14, 10:30 UTCJun 14, 11:30 UTC1h 0m
2026-06-10 STL29 - Jun 10, 11:35 UTCJun 10, 12:25 UTC50m
2026-06-10 STL02 - Jun 10, 09:45 UTCJun 10, 10:40 UTC55m

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 G-FULL page for operator, model, and routing details .

Mode-S 4021CF frequently asked

What is Mode-S code 4021CF?
4021CF is an ICAO 24-bit transponder address. Allocated to United Kingdom. Assigned to G-FULL.
Where is Mode-S 4021CF registered?
Mode-S code 4021CF is allocated to United Kingdom (GB). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4021CF broadcasting right now?
No active broadcast right now. Last signal was 13h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4021CF, octal 20020717, decimal 4,202,959.
What flights does 4021CF operate?
Mode-S 4021CF has broadcast 6 distinct callsigns, including STL29, STL36, STL02, GBNUT, STL18.