sensors Mode-S transponder

4D0121

ICAO 24-bit transponder address · allocated to Luxembourg

Currently assigned to LX-AFA · AIR TRACTOR AT-802

Hex
4D0121
Octal
23200441
Decimal
5,046,561
Country
LU
Tail
LX-AFA
Type
AT8T
No current signal · last broadcast 13h ago
Flights observed
10
Distinct callsigns
1
Country
LU
Last broadcast
13h ago

Last known position

Most recent position reported by Mode-S 4D0121.

Country allocation

The ICAO 24-bit address 4D0121 falls within the block assigned to Luxembourg (LU) by ICAO Annex 10, Volume III. Every aircraft registered in Luxembourg 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 1 distinct

Callsign Airline Flights Last seen
LXAFA - 10 2026-04-14

Recent flights last 10

DateFlightRouteTakeoffLandingDuration
2026-04-14 LXAFA - Apr 14, 09:10 UTCApr 14, 10:00 UTC50m
2026-04-14 LXAFA - Apr 14, 08:45 UTCApr 14, 09:05 UTC20m
2026-04-14 LXAFA - Apr 14, 07:10 UTCApr 14, 07:50 UTC40m
2026-04-14 LXAFA - Apr 14, 06:45 UTCApr 14, 07:10 UTC25m
2026-04-13 LXAFA - Apr 13, 15:45 UTCApr 13, 15:55 UTC10m
2026-04-13 LXAFA - Apr 13, 14:30 UTCApr 13, 15:05 UTC35m
2026-04-13 LXAFA - Apr 13, 13:15 UTCApr 13, 13:25 UTC10m
2026-04-13 LXAFA - Apr 13, 12:20 UTCApr 13, 12:45 UTC25m
2026-04-13 LXAFA - Apr 13, 09:30 UTCApr 13, 10:00 UTC30m
2026-04-13 LXAFA - Apr 13, 06:35 UTCApr 13, 07:55 UTC1h 20m

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 LX-AFA page for operator, model, and routing details .

Mode-S 4D0121 frequently asked

What is Mode-S code 4D0121?
4D0121 is an ICAO 24-bit transponder address. Allocated to Luxembourg. Assigned to LX-AFA.
Where is Mode-S 4D0121 registered?
Mode-S code 4D0121 is allocated to Luxembourg (LU). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4D0121 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 4D0121, octal 23200441, decimal 5,046,561.
What flights does 4D0121 operate?
Mode-S 4D0121 has broadcast 1 distinct callsign, including LXAFA.