Apparatus

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sensors Mode-S transponder

A546C9

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N439YX · EMBRAER ERJ-170-200 (long wing) · operated by REPUBLIC AIRWAYS INC

Hex
A546C9
Octal
51243311
Decimal
10,831,561
Country
US
Tail
N439YX
Type
E75L
No current signal · last broadcast Jul 26, 21:00 UTC
Flights observed
549
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:00 UTC

Last known position

Most recent position reported by Mode-S A546C9.

Country allocation

The ICAO 24-bit address A546C9 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 20 distinct

Callsign Airline Flights Last seen
RPA4537 Republic Airlines 12 2026-07-21
RPA4685 - 10 2026-07-16
RPA4413 Republic Airlines 10 2026-07-25
RPA4668 Republic Airlines 9 2026-07-24
RPA4500 - 9 2026-07-04
RPA4745 - 8 2026-06-18
RPA4676 Republic Airlines 8 2026-06-12
RPA4781 - 7 2026-07-16
RPA4729 Republic Airlines 7 2026-07-26
RPA4426 - 7 2026-07-19
RPA4383 - 7 2026-06-19
RPA4748 Republic Airlines 6 2026-07-23
RPA4746 - 6 2026-06-30
RPA4709 - 6 2026-07-13
RPA4665 Republic Airlines 6 2026-07-24
RPA4618 - 6 2026-07-09
RPA4496 Republic Airlines 6 2026-06-05
RPA4478 - 6 2026-07-02
RPA4469 Republic Airlines 6 2026-07-25
RPA4445 Republic Airlines 6 2026-07-01

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 RPA4370 PHL → BNA Jul 26, 20:15 UTCJul 26, 20:55 UTC40m
2026-07-26 RPA4367 DCA → PVD Jul 26, 18:10 UTCJul 26, 19:10 UTC1h 0m
2026-07-26 RPA4666 PIT → LGA Jul 26, 15:05 UTCJul 26, 16:10 UTC1h 5m
2026-07-26 RPA4666 PIT → LGA Jul 26, 12:50 UTCJul 26, 13:50 UTC1h 0m
2026-07-26 RPA4714 RDU → DCA Jul 26, 10:40 UTCJul 26, 11:40 UTC1h 0m
2026-07-26 RPA4640 JFK → PIT Jul 26, 02:50 UTCJul 26, 04:05 UTC1h 15m
2026-07-26 RPA4640 JFK → PIT Jul 26, 02:45 UTCJul 26, 04:04 UTC1h 19m
2026-07-26 RPA4729 CHS → DCA Jul 26, 00:05 UTCJul 26, 00:35 UTC30m
2026-07-25 RPA4729 CHS → DCA Jul 25, 22:35 UTCJul 25, 23:10 UTC35m
2026-07-25 RPA4469 PIT → DCA Jul 25, 19:50 UTCJul 25, 20:40 UTC50m
2026-07-25 RPA4469 PIT → DCA Jul 25, 19:45 UTCJul 25, 20:38 UTC53m
2026-07-25 RPA4469 PIT → DCA Jul 25, 17:40 UTCJul 25, 18:30 UTC50m
2026-07-25 RPA4413 DCA → PHL Jul 25, 14:15 UTCJul 25, 15:35 UTC1h 20m
2026-07-25 RPA4413 DCA → PHL Jul 25, 12:00 UTCJul 25, 13:05 UTC1h 5m
2026-07-25 RPA4362 DCA → LGA Jul 25, 09:45 UTCJul 25, 10:25 UTC40m
2026-07-25 RPA4594 MCI → LGA Jul 25, 02:00 UTCJul 25, 02:35 UTC35m
2026-07-24 RPA4668 PVD → DCA Jul 24, 23:10 UTCJul 25, 00:05 UTC55m
2026-07-24 RPA4668 PVD → DCA Jul 24, 21:05 UTCJul 24, 21:50 UTC45m
2026-07-24 RPA4665 JFK → RDU Jul 24, 17:10 UTCJul 24, 19:20 UTC2h 10m
2026-07-24 RPA4665 JFK → RDU Jul 24, 14:40 UTCJul 24, 16:20 UTC1h 40m
2026-07-24 RPA4512 LGA → OMA Jul 24, 10:20 UTCJul 24, 11:40 UTC1h 20m
2026-07-24 RPA4511 OMA → LGA Jul 24, 02:10 UTCJul 24, 03:20 UTC1h 10m
2026-07-23 RPA4668 PVD → DCA Jul 23, 23:30 UTCJul 24, 00:25 UTC55m
2026-07-23 RPA4668 PVD → DCA Jul 23, 21:35 UTCJul 23, 22:20 UTC45m
2026-07-23 RPA4748 DCA → ACK Jul 23, 17:40 UTCJul 23, 19:45 UTC2h 5m
2026-07-23 RPA4748 DCA → ACK Jul 23, 17:39 UTCJul 23, 19:44 UTC2h 5m
2026-07-23 RPA4748 DCA → ACK Jul 23, 14:15 UTCJul 23, 16:00 UTC1h 45m
2026-07-23 RPA4444 JFK → PIT Jul 23, 11:20 UTCJul 23, 12:15 UTC55m
2026-07-23 RPA4444 JFK → PIT Jul 23, 11:19 UTCJul 23, 12:14 UTC55m
2026-07-23 RPA4472 PHL → ATL Jul 23, 04:05 UTCJul 23, 05:10 UTC1h 5m
2026-07-23 RPA4472 PHL → ATL Jul 23, 04:01 UTCJul 23, 05:07 UTC1h 6m
2026-07-23 RPA4717 ILM → LGA Jul 23, 00:45 UTCJul 23, 02:35 UTC1h 50m
2026-07-22 RPA4717 ILM → LGA Jul 22, 22:55 UTCJul 22, 23:25 UTC30m
2026-07-22 RPA4717 ILM → LGA Jul 22, 22:05 UTCJul 22, 22:50 UTC45m
2026-07-22 RPA4720 MCI → LGA Jul 22, 19:10 UTCJul 22, 20:15 UTC1h 5m
2026-07-22 RPA4720 MCI → LGA Jul 22, 17:20 UTCJul 22, 18:00 UTC40m
2026-07-22 RPA4413 - Jul 22, 14:15 UTCJul 22, 15:40 UTC1h 25m
2026-07-22 RPA4413 ORD → BUF Jul 22, 12:15 UTCJul 22, 13:20 UTC1h 5m
2026-07-22 RPA4594 MCI → LGA Jul 22, 03:15 UTCJul 22, 03:45 UTC30m
2026-07-22 RPA4594 MCI → LGA Jul 22, 03:12 UTCJul 22, 03:42 UTC30m
2026-07-21 RPA4537 RIC → LGA Jul 21, 23:00 UTCJul 21, 23:55 UTC55m
2026-07-21 RPA4537 RIC → LGA Jul 21, 22:59 UTCJul 21, 23:54 UTC55m
2026-07-21 RPA4537 RIC → LGA Jul 21, 20:40 UTCJul 21, 21:25 UTC45m
2026-07-21 RPA4488 LGA → ORF Jul 21, 16:30 UTCJul 21, 19:05 UTC2h 35m
2026-07-21 RPA4488 LGA → ORF Jul 21, 13:20 UTCJul 21, 15:05 UTC1h 45m
2026-07-21 RPA4597 CMH → BOS Jul 21, 10:40 UTCJul 21, 11:20 UTC40m
2026-07-21 RPA4363 JFK → CVG Jul 21, 03:50 UTCJul 21, 04:20 UTC30m
2026-07-21 RPA4363 JFK → CVG Jul 21, 03:45 UTCJul 21, 04:18 UTC33m
2026-07-20 RPA4774 PVD → DCA Jul 20, 23:50 UTCJul 21, 02:05 UTC2h 15m
2026-07-20 RPA4774 PVD → DCA Jul 20, 21:05 UTCJul 20, 22:55 UTC1h 50m

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 N439YX page for operator, model, and routing details .

Mode-S A546C9 frequently asked

What is Mode-S code A546C9?
A546C9 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N439YX.
Where is Mode-S A546C9 registered?
Mode-S code A546C9 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 A546C9 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:00 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A546C9, octal 51243311, decimal 10,831,561.
What flights does A546C9 operate?
Mode-S A546C9 has broadcast 20 distinct callsigns, including RPA4537, RPA4685, RPA4413, RPA4668, RPA4500.