Apparatus

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sensors Mode-S transponder

A1D521

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N217SP · operated by SAMARITANS PURSE

Hex
A1D521
Octal
50352441
Decimal
10,605,857
Country
US
Tail
N217SP
Type
K900
No current signal · last broadcast 12d ago
Flights observed
73
Distinct callsigns
1
Country
US
Last broadcast
12d ago

Last known position

Most recent position reported by Mode-S A1D521.

Country allocation

The ICAO 24-bit address A1D521 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
N217SP - 73 2026-07-23

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-23 N217SP ANC → SXQ Jul 23, 20:25 UTCJul 23, 20:55 UTC30m
2026-07-23 N217SP - Jul 23, 18:45 UTCJul 23, 19:25 UTC40m
2026-07-23 N217SP - Jul 23, 17:15 UTCJul 23, 18:05 UTC50m
2026-07-23 N217SP - Jul 23, 15:40 UTCJul 23, 16:05 UTC25m
2026-07-16 N217SP - Jul 16, 21:25 UTCJul 16, 22:00 UTC35m
2026-07-16 N217SP - Jul 16, 18:40 UTCJul 16, 19:40 UTC1h 0m
2026-07-16 N217SP - Jul 16, 15:35 UTCJul 16, 15:55 UTC20m
2026-07-09 N217SP ANC → SXQ Jul 9, 23:15 UTCJul 9, 23:35 UTC20m
2026-07-09 N217SP - Jul 9, 19:15 UTCJul 9, 19:55 UTC40m
2026-07-09 N217SP - Jul 9, 17:10 UTCJul 9, 18:10 UTC1h 0m
2026-07-04 N217SP - Jul 4, 20:40 UTCJul 4, 21:40 UTC1h 0m
2026-07-04 N217SP - Jul 4, 18:45 UTCJul 4, 19:25 UTC40m
2026-07-04 N217SP - Jul 4, 16:45 UTCJul 4, 17:10 UTC25m
2026-07-03 N217SP CDV → SXQ Jul 3, 00:35 UTCJul 3, 01:35 UTC1h 0m
2026-07-02 N217SP - Jul 2, 23:15 UTCJul 3, 00:15 UTC1h 0m
2026-07-02 N217SP ANC → SXQ Jul 2, 21:20 UTCJul 2, 21:45 UTC25m
2026-07-02 N217SP - Jul 2, 17:55 UTCJul 2, 18:45 UTC50m
2026-07-02 N217SP - Jul 2, 16:30 UTCJul 2, 17:20 UTC50m
2026-06-28 N217SP ANC → SXQ Jun 28, 00:04 UTCJun 28, 02:14 UTC2h 10m
2026-06-27 N217SP - Jun 27, 16:20 UTCJun 27, 18:20 UTC2h 0m
2026-06-27 N217SP - Jun 27, 14:45 UTCJun 27, 15:05 UTC20m
2026-06-25 N217SP ANC → SXQ Jun 25, 21:10 UTCJun 25, 21:29 UTC20m
2026-06-25 N217SP - Jun 25, 19:29 UTCJun 25, 19:59 UTC30m
2026-06-25 N217SP - Jun 25, 16:39 UTCJun 25, 17:20 UTC40m
2026-06-25 N217SP - Jun 25, 15:20 UTCJun 25, 15:44 UTC25m
2026-06-22 N217SP SXQ → SXQ Jun 22, 23:29 UTCJun 23, 00:00 UTC30m
2026-06-20 N217SP - Jun 20, 18:40 UTCJun 20, 19:29 UTC50m
2026-06-20 N217SP - Jun 20, 16:14 UTCJun 20, 16:55 UTC40m
2026-06-18 N217SP ANC → SXQ Jun 18, 19:40 UTCJun 18, 20:00 UTC20m
2026-06-18 N217SP - Jun 18, 18:15 UTCJun 18, 18:55 UTC40m
2026-06-18 N217SP - Jun 18, 17:00 UTCJun 18, 17:45 UTC45m
2026-06-11 N217SP ANC → SXQ Jun 11, 19:45 UTCJun 11, 20:15 UTC30m
2026-06-11 N217SP - Jun 11, 18:15 UTCJun 11, 18:55 UTC40m
2026-06-11 N217SP - Jun 11, 16:55 UTCJun 11, 17:40 UTC45m
2026-06-11 N217SP - Jun 11, 15:10 UTCJun 11, 15:40 UTC30m
2026-06-08 N217SP - Jun 8, 19:35 UTCJun 8, 20:00 UTC25m
2026-06-08 N217SP - Jun 8, 16:30 UTCJun 8, 17:05 UTC35m
2026-06-04 N217SP - Jun 4, 20:10 UTCJun 4, 20:40 UTC30m
2026-06-04 N217SP - Jun 4, 18:05 UTCJun 4, 18:45 UTC40m
2026-06-04 N217SP - Jun 4, 16:25 UTCJun 4, 16:45 UTC20m
2026-05-28 N217SP - May 28, 18:55 UTCMay 28, 19:20 UTC25m
2026-05-28 N217SP - May 28, 16:25 UTCMay 28, 16:55 UTC30m
2026-05-28 N217SP - May 28, 15:10 UTCMay 28, 15:30 UTC20m
2026-05-25 N217SP - May 25, 22:49 UTCMay 25, 23:54 UTC1h 5m
2026-05-25 N217SP - May 25, 19:15 UTCMay 25, 19:54 UTC40m
2026-05-23 N217SP - May 23, 17:15 UTCMay 23, 17:45 UTC30m
2026-05-22 N217SP - May 22, 23:05 UTCMay 23, 00:25 UTC1h 20m
2026-05-22 N217SP SXQ → CDV May 22, 19:25 UTCMay 22, 20:25 UTC1h 0m
2026-05-21 N217SP ANC → SXQ May 21, 23:00 UTCMay 21, 23:25 UTC25m
2026-05-21 N217SP - May 21, 19:20 UTCMay 21, 20:05 UTC45m

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 N217SP page for operator, model, and routing details .

Mode-S A1D521 frequently asked

What is Mode-S code A1D521?
A1D521 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N217SP.
Where is Mode-S A1D521 registered?
Mode-S code A1D521 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 A1D521 broadcasting right now?
No active broadcast right now. Last signal was 12d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1D521, octal 50352441, decimal 10,605,857.
What flights does A1D521 operate?
Mode-S A1D521 has broadcast 1 distinct callsign, including N217SP.