Apparatus

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sensors Mode-S transponder

A3951D

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N33SY · DIAMOND DA-40 Club Star · operated by N33SY LLC

Hex
A3951D
Octal
50712435
Decimal
10,720,541
Country
US
Tail
N33SY
Type
DA40
No current signal · last broadcast 11m ago
Flights observed
97
Distinct callsigns
1
Country
US
Last broadcast
11m ago

Last known position

Most recent position reported by Mode-S A3951D.

Country allocation

The ICAO 24-bit address A3951D 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 1 distinct

Callsign Airline Flights Last seen
N33SY - 97 2026-05-31

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-31 N33SY MHR → MHR May 31, 19:55 UTCMay 31, 21:15 UTC1h 20m
2026-05-31 N33SY APC → MHR May 31, 18:10 UTCMay 31, 18:40 UTC30m
2026-05-31 N33SY MHR → APC May 31, 16:35 UTCMay 31, 17:15 UTC40m
2026-05-30 N33SY - May 30, 17:55 UTCMay 30, 19:00 UTC1h 5m
2026-05-30 N33SY MHR → MHR May 30, 14:00 UTCMay 30, 15:40 UTC1h 40m
2026-05-28 N33SY MHR → MHR May 28, 18:50 UTCMay 28, 19:40 UTC50m
2026-05-26 N33SY MHR → MHR May 26, 14:35 UTCMay 26, 15:00 UTC25m
2026-05-25 N33SY MHR → MHR May 25, 18:10 UTCMay 25, 19:05 UTC55m
2026-05-23 N33SY MHR → MHR May 23, 18:55 UTCMay 23, 20:45 UTC1h 50m
2026-05-23 N33SY MHR → MHR May 23, 14:25 UTCMay 23, 15:15 UTC50m
2026-05-22 N33SY MHR → MHR May 22, 20:25 UTCMay 22, 21:20 UTC55m
2026-05-22 N33SY MHR → MHR May 22, 14:40 UTCMay 22, 15:10 UTC30m
2026-05-20 N33SY - May 20, 17:05 UTCMay 20, 17:30 UTC25m
2026-05-19 N33SY MHR → MHR May 19, 17:05 UTCMay 19, 18:20 UTC1h 15m
2026-05-15 N33SY MHR → MHR May 15, 18:40 UTCMay 15, 19:35 UTC55m
2026-05-14 N33SY MHR → MHR May 14, 19:55 UTCMay 14, 21:05 UTC1h 10m
2026-05-14 N33SY MHR → MHR May 14, 17:30 UTCMay 14, 18:25 UTC55m
2026-05-13 N33SY MHR → MHR May 13, 23:40 UTCMay 14, 00:50 UTC1h 10m
2026-05-13 N33SY MHR → MHR May 13, 14:45 UTCMay 13, 15:15 UTC30m
2026-05-13 N33SY - May 13, 01:20 UTCMay 13, 01:45 UTC25m
2026-05-12 N33SY - May 12, 23:01 UTCMay 12, 23:40 UTC40m
2026-05-12 N33SY - May 12, 19:05 UTCMay 12, 20:01 UTC55m
2026-05-12 N33SY MHR → MHR May 12, 14:35 UTCMay 12, 15:40 UTC1h 5m
2026-05-11 N33SY MHR → MHR May 11, 21:10 UTCMay 11, 22:05 UTC55m
2026-05-11 N33SY MHR → MHR May 11, 18:30 UTCMay 11, 19:35 UTC1h 5m
2026-05-11 N33SY MHR → MHR May 11, 16:40 UTCMay 11, 17:30 UTC51m
2026-05-11 N33SY MHR → MHR May 11, 14:45 UTCMay 11, 15:30 UTC45m
2026-05-10 N33SY - May 10, 16:10 UTCMay 10, 17:05 UTC55m
2026-05-10 N33SY MHR → MHR May 10, 15:55 UTCMay 10, 16:04 UTC10m
2026-05-08 N33SY MHR → MHR May 8, 19:05 UTCMay 8, 19:45 UTC40m
2026-05-08 N33SY MHR → MHR May 8, 16:45 UTCMay 8, 18:30 UTC1h 45m
2026-05-07 N33SY MHR → MHR May 7, 22:54 UTCMay 7, 23:39 UTC45m
2026-05-07 N33SY MHR → MHR May 7, 20:35 UTCMay 7, 22:05 UTC1h 30m
2026-05-07 N33SY MHR → MHR May 7, 18:50 UTCMay 7, 19:30 UTC40m
2026-05-06 N33SY MHR → MHR May 6, 23:35 UTCMay 7, 00:30 UTC55m
2026-05-06 N33SY MHR → MHR May 6, 20:25 UTCMay 6, 21:30 UTC1h 5m
2026-05-06 N33SY MHR → MHR May 6, 18:05 UTCMay 6, 18:40 UTC35m
2026-05-06 N33SY MHR → MHR May 6, 16:55 UTCMay 6, 17:45 UTC49m
2026-05-06 N33SY MHR → MHR May 6, 14:40 UTCMay 6, 15:50 UTC1h 10m
2026-05-05 N33SY MHR → MHR May 5, 23:35 UTCMay 6, 01:35 UTC2h 0m
2026-05-04 N33SY MHR → MHR May 4, 16:30 UTCMay 4, 18:00 UTC1h 30m
2026-05-02 N33SY MHR → MHR May 2, 21:40 UTCMay 2, 22:50 UTC1h 10m
2026-05-02 N33SY - May 2, 18:55 UTCMay 2, 20:00 UTC1h 5m
2026-05-02 N33SY MHR → MHR May 2, 01:25 UTCMay 2, 02:15 UTC50m
2026-05-01 N33SY MHR → MHR May 1, 15:40 UTCMay 1, 17:25 UTC1h 45m
2026-05-01 N33SY - May 1, 00:05 UTCMay 1, 00:40 UTC35m
2026-04-30 N33SY - Apr 30, 20:20 UTCApr 30, 21:00 UTC40m
2026-04-30 N33SY - Apr 30, 18:20 UTCApr 30, 19:10 UTC50m
2026-04-30 N33SY - Apr 30, 15:55 UTCApr 30, 17:10 UTC1h 15m
2026-04-30 N33SY MHR → MHR Apr 30, 02:10 UTCApr 30, 02:35 UTC25m

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 N33SY page for operator, model, and routing details .

Mode-S A3951D frequently asked

What is Mode-S code A3951D?
A3951D is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N33SY.
Where is Mode-S A3951D registered?
Mode-S code A3951D 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 A3951D broadcasting right now?
No active broadcast right now. Last signal was 11m ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A3951D, octal 50712435, decimal 10,720,541.
What flights does A3951D operate?
Mode-S A3951D has broadcast 1 distinct callsign, including N33SY.