Apparatus

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sensors Mode-S transponder

A481FD

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N39RX · AIRBUS HELICOPTERS EC-135/635 · operated by REACH AIR MEDICAL SERVICES LLC

Hex
A481FD
Octal
51100775
Decimal
10,781,181
Country
US
Tail
N39RX
Type
EC35
No current signal · last broadcast 14h ago
Flights observed
175
Distinct callsigns
4
Country
US
Last broadcast
14h ago

Last known position

Most recent position reported by Mode-S A481FD.

Country allocation

The ICAO 24-bit address A481FD falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States 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 4 distinct

Callsign Airline Flights Last seen
REH43 - 156 2026-07-18
CMD3 - 12 2026-04-20
REH95 - 4 2026-05-23
RCH95 - 3 2026-05-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-18 REH43 - Jul 18, 03:05 UTCJul 18, 03:15 UTC10m
2026-07-18 REH43 - Jul 18, 02:00 UTCJul 18, 02:35 UTC35m
2026-07-16 REH43 - Jul 16, 23:29 UTCJul 17, 00:04 UTC35m
2026-07-16 REH43 - Jul 16, 16:49 UTCJul 16, 17:00 UTC10m
2026-07-16 REH43 - Jul 16, 06:10 UTCJul 16, 06:20 UTC10m
2026-07-16 REH43 - Jul 16, 04:45 UTCJul 16, 05:30 UTC45m
2026-07-15 REH43 - Jul 15, 22:50 UTCJul 15, 23:00 UTC10m
2026-07-15 REH43 - Jul 15, 22:00 UTCJul 15, 22:10 UTC10m
2026-07-15 REH43 - Jul 15, 21:00 UTCJul 15, 21:10 UTC10m
2026-07-15 REH43 - Jul 15, 11:55 UTCJul 15, 13:05 UTC1h 10m
2026-07-15 REH43 - Jul 15, 05:35 UTCJul 15, 05:45 UTC10m
2026-07-15 REH43 - Jul 15, 04:20 UTCJul 15, 04:30 UTC10m
2026-07-15 REH43 - Jul 15, 00:30 UTCJul 15, 01:00 UTC30m
2026-07-13 REH43 - Jul 13, 01:25 UTCJul 13, 01:35 UTC10m
2026-07-12 REH43 - Jul 12, 21:35 UTCJul 12, 22:25 UTC50m
2026-07-12 REH43 - Jul 12, 08:25 UTCJul 12, 09:10 UTC45m
2026-07-11 REH43 - Jul 11, 18:20 UTCJul 11, 18:30 UTC10m
2026-07-11 REH43 - Jul 11, 17:00 UTCJul 11, 17:40 UTC40m
2026-07-10 REH43 - Jul 10, 23:25 UTCJul 10, 23:35 UTC10m
2026-07-10 REH43 - Jul 10, 21:55 UTCJul 10, 22:05 UTC10m
2026-07-09 REH43 - Jul 9, 05:35 UTCJul 9, 05:45 UTC10m
2026-07-09 REH43 - Jul 9, 01:45 UTCJul 9, 02:20 UTC35m
2026-07-09 REH43 - Jul 9, 01:00 UTCJul 9, 01:10 UTC10m
2026-07-08 REH43 - Jul 8, 19:05 UTCJul 8, 19:30 UTC25m
2026-07-08 REH43 - Jul 8, 02:20 UTCJul 8, 03:15 UTC55m
2026-07-07 REH43 - Jul 7, 10:15 UTCJul 7, 10:45 UTC30m
2026-07-07 REH43 - Jul 7, 00:35 UTCJul 7, 01:45 UTC1h 10m
2026-07-06 REH43 - Jul 6, 02:15 UTCJul 6, 03:25 UTC1h 10m
2026-07-05 REH43 - Jul 5, 20:40 UTCJul 5, 21:55 UTC1h 15m
2026-07-04 REH43 - Jul 4, 06:45 UTCJul 4, 07:35 UTC50m
2026-07-04 REH43 - Jul 4, 04:20 UTCJul 4, 04:30 UTC10m
2026-07-04 REH43 - Jul 4, 02:45 UTCJul 4, 04:00 UTC1h 15m
2026-07-03 REH43 - Jul 3, 14:15 UTCJul 3, 14:25 UTC10m
2026-07-03 REH43 - Jul 3, 12:50 UTCJul 3, 13:00 UTC10m
2026-07-03 REH43 - Jul 3, 11:45 UTCJul 3, 12:00 UTC15m
2026-07-02 REH43 - Jul 2, 08:35 UTCJul 2, 08:50 UTC15m
2026-07-02 REH43 - Jul 2, 07:15 UTCJul 2, 07:55 UTC40m
2026-07-01 REH43 - Jul 1, 19:45 UTCJul 1, 20:05 UTC20m
2026-07-01 REH43 - Jul 1, 15:35 UTCJul 1, 15:55 UTC20m
2026-07-01 REH43 - Jul 1, 05:25 UTCJul 1, 05:40 UTC15m
2026-07-01 REH43 - Jul 1, 03:55 UTCJul 1, 04:10 UTC15m
2026-07-01 REH43 - Jul 1, 01:45 UTCJul 1, 01:55 UTC10m
2026-06-30 REH43 - Jun 30, 20:55 UTCJun 30, 21:05 UTC10m
2026-06-30 REH43 - Jun 30, 20:05 UTCJun 30, 20:20 UTC15m
2026-06-29 REH43 - Jun 29, 18:30 UTCJun 29, 18:49 UTC20m
2026-06-29 REH43 - Jun 29, 17:14 UTCJun 29, 17:59 UTC45m
2026-06-29 REH43 - Jun 29, 09:00 UTCJun 29, 09:40 UTC40m
2026-06-29 REH43 - Jun 29, 08:19 UTCJun 29, 08:44 UTC25m
2026-06-29 REH43 - Jun 29, 00:00 UTCJun 29, 00:10 UTC10m
2026-06-28 REH43 - Jun 28, 23:20 UTCJun 28, 23:29 UTC10m

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 N39RX page for operator, model, and routing details .

Mode-S A481FD frequently asked

What is Mode-S code A481FD?
A481FD is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N39RX.
Where is Mode-S A481FD registered?
Mode-S code A481FD is allocated to United States (US). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is A481FD broadcasting right now?
No active broadcast right now. Last signal was 14h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A481FD, octal 51100775, decimal 10,781,181.
What flights does A481FD operate?
Mode-S A481FD has broadcast 4 distinct callsigns, including REH43, CMD3, REH95, RCH95.