Apparatus

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sensors Mode-S transponder

A1D685

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N21745 · CESSNA 172 Skyhawk · operated by BELLINGHAM AVIATION SERVICES LLC

Hex
A1D685
Octal
50353205
Decimal
10,606,213
Country
US
Tail
N21745
Type
C172
No current signal · last broadcast 3h ago
Flights observed
172
Distinct callsigns
1
Country
US
Last broadcast
3h ago

Last known position

Most recent position reported by Mode-S A1D685.

Country allocation

The ICAO 24-bit address A1D685 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
N21745 - 172 2026-07-20

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-20 N21745 BLI → BLI Jul 20, 19:45 UTCJul 20, 20:40 UTC55m
2026-07-20 N21745 - Jul 20, 17:55 UTCJul 20, 18:35 UTC40m
2026-07-20 N21745 - Jul 20, 02:50 UTCJul 20, 05:00 UTC2h 10m
2026-07-19 N21745 - Jul 19, 02:50 UTCJul 19, 05:25 UTC2h 35m
2026-07-18 N21745 BLI → BLI Jul 18, 22:25 UTCJul 18, 22:50 UTC25m
2026-07-18 N21745 - Jul 18, 17:50 UTCJul 18, 18:40 UTC50m
2026-07-17 N21745 BLI → BLI Jul 17, 23:35 UTCJul 18, 01:39 UTC2h 5m
2026-07-17 N21745 - Jul 17, 21:44 UTCJul 17, 22:40 UTC55m
2026-07-17 N21745 - Jul 17, 19:55 UTCJul 17, 20:29 UTC35m
2026-07-17 N21745 - Jul 17, 17:44 UTCJul 17, 18:50 UTC1h 5m
2026-07-16 N21745 BLI → BLI Jul 16, 17:45 UTCJul 16, 18:40 UTC55m
2026-07-16 N21745 BLI → BLI Jul 16, 15:49 UTCJul 16, 16:30 UTC40m
2026-07-16 N21745 - Jul 16, 01:50 UTCJul 16, 04:20 UTC2h 30m
2026-07-15 N21745 - Jul 15, 01:55 UTCJul 15, 03:45 UTC1h 50m
2026-07-14 N21745 - Jul 14, 23:50 UTCJul 15, 01:00 UTC1h 10m
2026-07-14 N21745 BLI → BLI Jul 14, 21:35 UTCJul 14, 22:25 UTC50m
2026-07-14 N21745 BLI → BLI Jul 14, 18:45 UTCJul 14, 19:45 UTC1h 0m
2026-07-14 N21745 - Jul 14, 15:50 UTCJul 14, 16:45 UTC55m
2026-07-13 N21745 - Jul 13, 17:45 UTCJul 13, 18:45 UTC1h 0m
2026-07-12 N21745 - Jul 12, 22:40 UTCJul 13, 00:20 UTC1h 40m
2026-07-12 N21745 - Jul 12, 17:20 UTCJul 12, 18:01 UTC40m
2026-07-11 N21745 - Jul 11, 20:55 UTCJul 11, 21:05 UTC10m
2026-07-11 N21745 - Jul 11, 20:10 UTCJul 11, 20:20 UTC10m
2026-07-11 N21745 - Jul 11, 02:45 UTCJul 11, 04:20 UTC1h 35m
2026-07-10 N21745 - Jul 10, 21:50 UTCJul 10, 22:45 UTC55m
2026-07-10 N21745 BLI → BLI Jul 10, 16:10 UTCJul 10, 16:35 UTC25m
2026-07-10 N21745 - Jul 10, 01:35 UTCJul 10, 02:50 UTC1h 15m
2026-07-09 N21745 - Jul 9, 23:45 UTCJul 10, 01:05 UTC1h 20m
2026-07-09 N21745 - Jul 9, 18:55 UTCJul 9, 19:05 UTC10m
2026-07-09 N21745 - Jul 9, 00:50 UTCJul 9, 01:55 UTC1h 5m
2026-07-08 N21745 - Jul 8, 22:10 UTCJul 8, 22:45 UTC35m
2026-07-07 N21745 - Jul 7, 23:45 UTCJul 8, 01:25 UTC1h 40m
2026-07-07 N21745 - Jul 7, 20:10 UTCJul 7, 21:25 UTC1h 15m
2026-07-04 N21745 BLI → BLI Jul 4, 18:30 UTCJul 4, 19:20 UTC50m
2026-07-01 N21745 BLI → BLI Jul 1, 19:00 UTCJul 1, 20:10 UTC1h 10m
2026-06-30 N21745 - Jun 30, 23:45 UTCJul 1, 00:20 UTC35m
2026-06-30 N21745 - Jun 30, 20:50 UTCJun 30, 21:30 UTC40m
2026-06-30 N21745 - Jun 30, 18:30 UTCJun 30, 18:50 UTC20m
2026-06-30 N21745 - Jun 30, 16:45 UTCJun 30, 17:35 UTC50m
2026-06-29 N21745 - Jun 29, 23:54 UTCJun 30, 00:49 UTC55m
2026-06-29 N21745 - Jun 29, 18:55 UTCJun 29, 20:15 UTC1h 20m
2026-06-28 N21745 FRD → BLI Jun 28, 01:50 UTCJun 28, 02:10 UTC20m
2026-06-27 N21745 - Jun 27, 20:39 UTCJun 27, 22:29 UTC1h 50m
2026-06-27 N21745 BLI → BLI Jun 27, 17:49 UTCJun 27, 18:45 UTC55m
2026-06-25 N21745 - Jun 25, 23:49 UTCJun 26, 00:50 UTC1h 0m
2026-06-25 N21745 BLI → BLI Jun 25, 17:30 UTCJun 25, 18:29 UTC1h 0m
2026-06-24 N21745 - Jun 24, 23:45 UTCJun 25, 00:44 UTC1h 0m
2026-06-24 N21745 - Jun 24, 22:04 UTCJun 24, 22:45 UTC40m
2026-06-24 N21745 - Jun 24, 19:49 UTCJun 24, 20:35 UTC45m
2026-06-24 N21745 BLI → BLI Jun 24, 17:45 UTCJun 24, 18:44 UTC1h 0m

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 N21745 page for operator, model, and routing details .

Mode-S A1D685 frequently asked

What is Mode-S code A1D685?
A1D685 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N21745.
Where is Mode-S A1D685 registered?
Mode-S code A1D685 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 A1D685 broadcasting right now?
No active broadcast right now. Last signal was 3h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1D685, octal 50353205, decimal 10,606,213.
What flights does A1D685 operate?
Mode-S A1D685 has broadcast 1 distinct callsign, including N21745.