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sensors Mode-S transponder

A660DC

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N51UD · CESSNA 172 Skyhawk · operated by ALF IX LLC

Hex
A660DC
Octal
51460334
Decimal
10,903,772
Country
US
Tail
N51UD
Type
C172
No current signal · last broadcast 4d ago
Flights observed
291
Distinct callsigns
1
Country
US
Last broadcast
4d ago

Last known position

Most recent position reported by Mode-S A660DC.

Country allocation

The ICAO 24-bit address A660DC 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
N51UD - 291 2026-07-10

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-10 N51UD AUO → AUO Jul 10, 14:10 UTCJul 10, 15:20 UTC1h 10m
2026-07-10 N51UD - Jul 10, 11:55 UTCJul 10, 13:10 UTC1h 15m
2026-07-09 N51UD AUO → AUO Jul 9, 13:50 UTCJul 9, 16:40 UTC2h 50m
2026-07-09 N51UD - Jul 9, 00:00 UTCJul 9, 01:20 UTC1h 20m
2026-07-08 N51UD - Jul 8, 22:25 UTCJul 8, 22:50 UTC25m
2026-07-08 N51UD - Jul 8, 21:20 UTCJul 8, 21:50 UTC30m
2026-07-08 N51UD AUO → AUO Jul 8, 16:40 UTCJul 8, 18:15 UTC1h 35m
2026-07-08 N51UD AUO → AUO Jul 8, 14:00 UTCJul 8, 15:40 UTC1h 40m
2026-07-07 N51UD - Jul 7, 18:35 UTCJul 7, 20:10 UTC1h 35m
2026-07-07 N51UD AUO → AUO Jul 7, 14:10 UTCJul 7, 15:40 UTC1h 30m
2026-07-07 N51UD AUO → AUO Jul 7, 12:00 UTCJul 7, 13:15 UTC1h 15m
2026-07-03 N51UD AUO → AUO Jul 3, 22:45 UTCJul 3, 22:50 UTC5m
2026-07-03 N51UD - Jul 3, 21:55 UTCJul 3, 22:40 UTC45m
2026-07-03 N51UD AUO → AUO Jul 3, 21:35 UTCJul 3, 21:40 UTC5m
2026-07-03 N51UD AUO → AUO Jul 3, 18:45 UTCJul 3, 20:00 UTC1h 15m
2026-07-03 N51UD AUO → AUO Jul 3, 11:40 UTCJul 3, 13:40 UTC2h 0m
2026-07-03 N51UD AUO → AUO Jul 3, 02:35 UTCJul 3, 04:00 UTC1h 25m
2026-07-02 N51UD AUO → AUO Jul 2, 23:50 UTCJul 3, 01:20 UTC1h 30m
2026-07-02 N51UD - Jul 2, 21:20 UTCJul 2, 22:40 UTC1h 20m
2026-07-02 N51UD - Jul 2, 20:20 UTCJul 2, 20:30 UTC10m
2026-07-02 N51UD - Jul 2, 18:50 UTCJul 2, 19:00 UTC10m
2026-07-02 N51UD AUO → AUO Jul 2, 16:40 UTCJul 2, 17:40 UTC1h 0m
2026-07-02 N51UD - Jul 2, 11:45 UTCJul 2, 13:50 UTC2h 5m
2026-07-01 N51UD - Jul 1, 20:00 UTCJul 1, 20:10 UTC10m
2026-07-01 N51UD - Jul 1, 17:05 UTCJul 1, 17:15 UTC10m
2026-07-01 N51UD - Jul 1, 14:15 UTCJul 1, 15:55 UTC1h 40m
2026-07-01 N51UD AUO → AUO Jul 1, 11:55 UTCJul 1, 13:20 UTC1h 25m
2026-07-01 N51UD - Jul 1, 03:45 UTCJul 1, 03:50 UTC5m
2026-07-01 N51UD AUO → AUO Jul 1, 03:10 UTCJul 1, 03:30 UTC20m
2026-07-01 N51UD AUO → AUO Jul 1, 02:45 UTCJul 1, 02:55 UTC10m
2026-07-01 N51UD AUO → AUO Jul 1, 02:20 UTCJul 1, 02:25 UTC5m
2026-06-30 N51UD AUO → AUO Jun 30, 21:10 UTCJun 30, 22:40 UTC1h 30m
2026-06-30 N51UD AUO → AUO Jun 30, 18:55 UTCJun 30, 20:10 UTC1h 15m
2026-06-30 N51UD - Jun 30, 15:50 UTCJun 30, 16:15 UTC25m
2026-06-30 N51UD - Jun 30, 14:20 UTCJun 30, 14:45 UTC25m
2026-06-30 N51UD AUO → AUO Jun 30, 13:20 UTCJun 30, 13:30 UTC10m
2026-06-30 N51UD AUO → AUO Jun 30, 11:45 UTCJun 30, 13:15 UTC1h 30m
2026-06-29 N51UD AUO → AUO Jun 29, 23:19 UTCJun 30, 00:49 UTC1h 30m
2026-06-29 N51UD AUO → AUO Jun 29, 21:24 UTCJun 29, 22:39 UTC1h 15m
2026-06-29 N51UD - Jun 29, 17:45 UTCJun 29, 17:49 UTC5m
2026-06-29 N51UD - Jun 29, 16:35 UTCJun 29, 16:55 UTC20m
2026-06-29 N51UD - Jun 29, 15:39 UTCJun 29, 16:15 UTC35m
2026-06-29 N51UD - Jun 29, 14:54 UTCJun 29, 15:04 UTC10m
2026-06-28 N51UD - Jun 28, 14:19 UTCJun 28, 14:39 UTC20m
2026-06-27 N51UD AUO → AUO Jun 27, 20:34 UTCJun 27, 21:59 UTC1h 25m
2026-06-27 N51UD - Jun 27, 19:15 UTCJun 27, 19:39 UTC25m
2026-06-27 N51UD - Jun 27, 18:29 UTCJun 27, 18:39 UTC10m
2026-06-25 N51UD AUO → AUO Jun 25, 17:54 UTCJun 25, 18:00 UTC5m
2026-06-25 N51UD - Jun 25, 16:45 UTCJun 25, 16:55 UTC10m
2026-06-25 N51UD - Jun 25, 14:29 UTCJun 25, 15:59 UTC1h 30m

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 N51UD page for operator, model, and routing details .

Mode-S A660DC frequently asked

What is Mode-S code A660DC?
A660DC is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N51UD.
Where is Mode-S A660DC registered?
Mode-S code A660DC 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 A660DC broadcasting right now?
No active broadcast right now. Last signal was 4d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A660DC, octal 51460334, decimal 10,903,772.
What flights does A660DC operate?
Mode-S A660DC has broadcast 1 distinct callsign, including N51UD.