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sensors Mode-S transponder

4051B1

ICAO 24-bit transponder address · allocated to United Kingdom

Currently assigned to G-SFLA · IKARUS C-42 Bison

Hex
4051B1
Octal
20050661
Decimal
4,215,217
Country
GB
Tail
G-SFLA
Type
C42
No current signal · last broadcast 10h ago
Flights observed
193
Distinct callsigns
3
Country
GB
Last broadcast
10h ago

Last known position

Most recent position reported by Mode-S 4051B1.

Country allocation

The ICAO 24-bit address 4051B1 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 3 distinct

Callsign Airline Flights Last seen
GSFLA - 182 2026-07-17
SFU55 - 9 2026-07-16
SFU71 - 2 2026-06-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-17 GSFLA - Jul 17, 15:55 UTCJul 17, 16:44 UTC50m
2026-07-17 GSFLA - Jul 17, 11:25 UTCJul 17, 12:10 UTC45m
2026-07-17 GSFLA - Jul 17, 10:55 UTCJul 17, 11:20 UTC25m
2026-07-17 GSFLA - Jul 17, 09:30 UTCJul 17, 09:40 UTC10m
2026-07-17 GSFLA - Jul 17, 08:25 UTCJul 17, 09:20 UTC55m
2026-07-16 SFU55 - Jul 16, 16:00 UTCJul 16, 16:40 UTC40m
2026-07-16 SFU55 - Jul 16, 15:05 UTCJul 16, 15:19 UTC15m
2026-07-16 GSFLA - Jul 16, 12:05 UTCJul 16, 13:49 UTC1h 45m
2026-07-16 GSFLA - Jul 16, 10:29 UTCJul 16, 11:25 UTC55m
2026-07-16 GSFLA - Jul 16, 09:25 UTCJul 16, 09:45 UTC20m
2026-07-16 GSFLA - Jul 16, 08:25 UTCJul 16, 08:45 UTC20m
2026-07-15 GSFLA - Jul 15, 16:10 UTCJul 15, 16:55 UTC45m
2026-07-14 GSFLA - Jul 14, 11:50 UTCJul 14, 13:00 UTC1h 10m
2026-07-14 GSFLA - Jul 14, 10:50 UTCJul 14, 11:00 UTC10m
2026-07-14 GSFLA - Jul 14, 09:20 UTCJul 14, 09:35 UTC15m
2026-07-11 GSFLA - Jul 11, 13:15 UTCJul 11, 14:00 UTC45m
2026-07-11 GSFLA - Jul 11, 11:25 UTCJul 11, 12:35 UTC1h 10m
2026-07-11 GSFLA - Jul 11, 10:25 UTCJul 11, 10:35 UTC10m
2026-07-11 GSFLA - Jul 11, 09:05 UTCJul 11, 09:55 UTC50m
2026-07-11 GSFLA - Jul 11, 08:15 UTCJul 11, 08:25 UTC10m
2026-07-10 GSFLA - Jul 10, 15:55 UTCJul 10, 16:55 UTC1h 0m
2026-07-10 GSFLA - Jul 10, 10:55 UTCJul 10, 14:10 UTC3h 15m
2026-07-10 GSFLA - Jul 10, 08:30 UTCJul 10, 09:35 UTC1h 5m
2026-07-09 GSFLA - Jul 9, 17:20 UTCJul 9, 17:35 UTC15m
2026-07-09 GSFLA - Jul 9, 15:55 UTCJul 9, 16:10 UTC15m
2026-07-09 GSFLA - Jul 9, 14:50 UTCJul 9, 15:25 UTC35m
2026-07-09 GSFLA - Jul 9, 13:20 UTCJul 9, 13:45 UTC25m
2026-07-09 GSFLA - Jul 9, 12:45 UTCJul 9, 12:55 UTC10m
2026-07-09 GSFLA - Jul 9, 11:30 UTCJul 9, 12:05 UTC35m
2026-07-09 GSFLA - Jul 9, 10:10 UTCJul 9, 10:50 UTC40m
2026-07-09 GSFLA - Jul 9, 08:15 UTCJul 9, 09:25 UTC1h 10m
2026-07-08 GSFLA - Jul 8, 16:40 UTCJul 8, 17:35 UTC55m
2026-07-08 GSFLA - Jul 8, 15:10 UTCJul 8, 16:00 UTC50m
2026-07-08 GSFLA - Jul 8, 13:35 UTCJul 8, 14:10 UTC35m
2026-07-08 GSFLA - Jul 8, 11:15 UTCJul 8, 12:15 UTC1h 0m
2026-07-08 GSFLA - Jul 8, 08:55 UTCJul 8, 09:40 UTC45m
2026-07-07 GSFLA - Jul 7, 10:50 UTCJul 7, 13:50 UTC3h 0m
2026-07-07 GSFLA - Jul 7, 09:10 UTCJul 7, 10:05 UTC55m
2026-07-05 GSFLA - Jul 5, 12:35 UTCJul 5, 13:40 UTC1h 5m
2026-07-05 GSFLA - Jul 5, 08:45 UTCJul 5, 10:05 UTC1h 20m
2026-07-04 GSFLA - Jul 4, 14:25 UTCJul 4, 15:10 UTC45m
2026-07-04 GSFLA - Jul 4, 12:30 UTCJul 4, 13:20 UTC50m
2026-07-04 GSFLA - Jul 4, 10:40 UTCJul 4, 11:35 UTC55m
2026-07-03 GSFLA - Jul 3, 14:00 UTCJul 3, 16:35 UTC2h 35m
2026-07-03 GSFLA - Jul 3, 09:55 UTCJul 3, 10:35 UTC40m
2026-07-03 GSFLA - Jul 3, 08:40 UTCJul 3, 08:50 UTC10m
2026-07-02 GSFLA - Jul 2, 15:30 UTCJul 2, 15:50 UTC20m
2026-07-02 GSFLA - Jul 2, 13:40 UTCJul 2, 14:00 UTC20m
2026-07-02 GSFLA - Jul 2, 10:55 UTCJul 2, 11:05 UTC10m
2026-07-01 GSFLA - Jul 1, 15:35 UTCJul 1, 16:20 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 G-SFLA page for operator, model, and routing details .

Mode-S 4051B1 frequently asked

What is Mode-S code 4051B1?
4051B1 is an ICAO 24-bit transponder address. Allocated to United Kingdom. Assigned to G-SFLA.
Where is Mode-S 4051B1 registered?
Mode-S code 4051B1 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 4051B1 broadcasting right now?
No active broadcast right now. Last signal was 10h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4051B1, octal 20050661, decimal 4,215,217.
What flights does 4051B1 operate?
Mode-S 4051B1 has broadcast 3 distinct callsigns, including GSFLA, SFU55, SFU71.