sensors Mode-S transponder

4D2191

ICAO 24-bit transponder address · allocated to Malta

Currently assigned to 9H-OJJ · BOMBARDIER CL-600 Challenger

Hex
4D2191
Octal
23220621
Decimal
5,054,865
Country
MT
Tail
9H-OJJ
Type
CL60
No current signal · last broadcast 1d ago
Flights observed
1
Distinct callsigns
1
Country
MT
Last broadcast
1d ago

Last known position

Most recent position reported by Mode-S 4D2191.

Country allocation

The ICAO 24-bit address 4D2191 falls within the block assigned to Malta (MT) by ICAO Annex 10, Volume III. Every aircraft registered in Malta 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
ULC7P - 1 2026-04-14

Recent flights last 1

DateFlightRouteTakeoffLandingDuration
2026-04-14 ULC7P - Apr 14, 07:10 UTCApr 14, 08:45 UTC1h 35m

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 9H-OJJ page for operator, model, and routing details .

Mode-S 4D2191 frequently asked

What is Mode-S code 4D2191?
4D2191 is an ICAO 24-bit transponder address. Allocated to Malta. Assigned to 9H-OJJ.
Where is Mode-S 4D2191 registered?
Mode-S code 4D2191 is allocated to Malta (MT). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4D2191 broadcasting right now?
No active broadcast right now. Last signal was 1d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4D2191, octal 23220621, decimal 5,054,865.
What flights does 4D2191 operate?
Mode-S 4D2191 has broadcast 1 distinct callsign, including ULC7P.