Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

0AC9B4

ICAO 24-bit transponder address · allocated to Costa Rica

Currently assigned to HK-4991 · CESSNA 208 Caravan

Hex
0AC9B4
Octal
02544664
Decimal
706,996
Country
CR
Tail
HK-4991
Type
C208
No current signal · last broadcast 4h ago
Flights observed
54
Distinct callsigns
1
Country
CR
Last broadcast
4h ago

Last known position

Most recent position reported by Mode-S 0AC9B4.

Country allocation

The ICAO 24-bit address 0AC9B4 falls within the block assigned to Costa Rica (CR) by ICAO Annex 10, Volume III. Every aircraft registered in Costa Rica 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
HK4991 - 54 2026-06-29

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-06-29 HK4991 - Jun 29, 16:44 UTCJun 29, 17:34 UTC50m
2026-06-28 HK4991 - Jun 28, 17:55 UTCJun 28, 18:44 UTC50m
2026-06-28 HK4991 - Jun 28, 13:34 UTCJun 28, 14:30 UTC55m
2026-06-26 HK4991 - Jun 26, 20:40 UTCJun 26, 21:30 UTC50m
2026-06-26 HK4991 - Jun 26, 17:09 UTCJun 26, 17:54 UTC45m
2026-06-26 HK4991 - Jun 26, 15:25 UTCJun 26, 16:00 UTC35m
2026-06-26 HK4991 - Jun 26, 12:44 UTCJun 26, 13:34 UTC50m
2026-06-25 HK4991 - Jun 25, 18:24 UTCJun 25, 18:50 UTC25m
2026-06-25 HK4991 - Jun 25, 15:59 UTCJun 25, 17:44 UTC1h 45m
2026-06-25 HK4991 - Jun 25, 13:00 UTCJun 25, 14:09 UTC1h 10m
2026-06-24 HK4991 - Jun 24, 21:44 UTCJun 24, 22:25 UTC40m
2026-06-24 HK4991 - Jun 24, 19:34 UTCJun 24, 20:30 UTC55m
2026-06-23 HK4991 - Jun 23, 19:04 UTCJun 23, 19:55 UTC50m
2026-06-23 HK4991 - Jun 23, 15:24 UTCJun 23, 16:09 UTC45m
2026-06-23 HK4991 LET → LET Jun 23, 12:29 UTCJun 23, 13:09 UTC40m
2026-06-22 HK4991 - Jun 22, 17:50 UTCJun 22, 18:24 UTC35m
2026-06-19 HK4991 - Jun 19, 11:49 UTCJun 19, 12:44 UTC55m
2026-06-18 HK4991 LET → LET Jun 18, 20:15 UTCJun 18, 21:45 UTC1h 30m
2026-06-18 HK4991 - Jun 18, 17:55 UTCJun 18, 18:55 UTC1h 0m
2026-06-18 HK4991 - Jun 18, 13:40 UTCJun 18, 14:25 UTC45m
2026-06-17 HK4991 - Jun 17, 19:35 UTCJun 17, 20:25 UTC50m
2026-06-17 HK4991 - Jun 17, 13:30 UTCJun 17, 14:20 UTC50m
2026-06-16 HK4991 - Jun 16, 15:35 UTCJun 16, 16:25 UTC50m
2026-06-02 HK4991 - Jun 2, 21:05 UTCJun 2, 21:15 UTC10m
2026-06-02 HK4991 - Jun 2, 17:10 UTCJun 2, 18:30 UTC1h 20m
2026-06-01 HK4991 LET → LET Jun 1, 20:05 UTCJun 1, 21:30 UTC1h 25m
2026-06-01 HK4991 - Jun 1, 18:55 UTCJun 1, 19:35 UTC40m
2026-06-01 HK4991 - Jun 1, 13:30 UTCJun 1, 14:35 UTC1h 5m
2026-05-30 HK4991 - May 30, 17:00 UTCMay 30, 17:45 UTC45m
2026-05-30 HK4991 - May 30, 13:25 UTCMay 30, 14:15 UTC50m
2026-05-28 HK4991 - May 28, 18:55 UTCMay 28, 19:45 UTC50m
2026-05-28 HK4991 - May 28, 13:45 UTCMay 28, 14:40 UTC55m
2026-05-27 HK4991 - May 27, 21:50 UTCMay 27, 22:15 UTC25m
2026-05-27 HK4991 - May 27, 19:45 UTCMay 27, 20:15 UTC30m
2026-05-27 HK4991 - May 27, 18:05 UTCMay 27, 18:55 UTC50m
2026-05-27 HK4991 - May 27, 13:55 UTCMay 27, 14:50 UTC55m
2026-05-25 HK4991 - May 25, 19:00 UTCMay 25, 19:44 UTC44m
2026-05-25 HK4991 - May 25, 14:55 UTCMay 25, 15:40 UTC45m
2026-05-24 HK4991 - May 24, 19:10 UTCMay 24, 19:40 UTC30m
2026-05-24 HK4991 - May 24, 16:40 UTCMay 24, 18:25 UTC1h 45m
2026-05-24 HK4991 - May 24, 13:20 UTCMay 24, 14:20 UTC1h 0m
2026-05-22 HK4991 - May 22, 20:05 UTCMay 22, 20:55 UTC50m
2026-05-22 HK4991 - May 22, 16:10 UTCMay 22, 16:20 UTC10m
2026-05-20 HK4991 - May 20, 12:00 UTCMay 20, 12:20 UTC20m
2026-05-18 HK4991 - May 18, 21:05 UTCMay 18, 21:20 UTC15m
2026-05-17 HK4991 - May 17, 13:05 UTCMay 17, 13:15 UTC10m
2026-05-15 HK4991 - May 15, 21:05 UTCMay 15, 21:15 UTC10m
2026-05-15 HK4991 - May 15, 20:05 UTCMay 15, 20:15 UTC10m
2026-05-15 HK4991 - May 15, 16:50 UTCMay 15, 17:00 UTC10m
2026-05-15 HK4991 - May 15, 14:15 UTCMay 15, 15:05 UTC49m

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 HK-4991 page for operator, model, and routing details .

Mode-S 0AC9B4 frequently asked

What is Mode-S code 0AC9B4?
0AC9B4 is an ICAO 24-bit transponder address. Allocated to Costa Rica. Assigned to HK-4991.
Where is Mode-S 0AC9B4 registered?
Mode-S code 0AC9B4 is allocated to Costa Rica (CR). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 0AC9B4 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 0AC9B4, octal 02544664, decimal 706,996.
What flights does 0AC9B4 operate?
Mode-S 0AC9B4 has broadcast 1 distinct callsign, including HK4991.