Apparatus

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sensors Mode-S transponder

A21E9D

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N23581 · CESSNA 172R Cutlass RG · operated by SO CAL LEASING LLC

Hex
A21E9D
Octal
50417235
Decimal
10,624,669
Country
US
Tail
N23581
Type
C72R
No current signal · last broadcast 13h ago
Flights observed
47
Distinct callsigns
1
Country
US
Last broadcast
13h ago

Last known position

Most recent position reported by Mode-S A21E9D.

Country allocation

The ICAO 24-bit address A21E9D 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
N23581 - 47 2026-05-29

Recent flights last 47

DateFlightRouteTakeoffLandingDuration
2026-05-29 N23581 - May 29, 20:15 UTCMay 29, 21:05 UTC50m
2026-05-28 N23581 SEE → SEE May 28, 21:50 UTCMay 28, 22:55 UTC1h 5m
2026-05-28 N23581 - May 28, 18:05 UTCMay 28, 19:00 UTC55m
2026-05-27 N23581 - May 27, 22:00 UTCMay 27, 22:55 UTC55m
2026-05-27 N23581 - May 27, 18:10 UTCMay 27, 18:55 UTC45m
2026-05-23 N23581 - May 23, 18:50 UTCMay 23, 20:00 UTC1h 10m
2026-05-22 N23581 - May 22, 19:45 UTCMay 22, 20:25 UTC40m
2026-05-22 N23581 SEE → HMT May 22, 17:55 UTCMay 22, 19:30 UTC1h 35m
2026-05-14 N23581 SEE → SEE May 14, 22:45 UTCMay 14, 23:35 UTC50m
2026-05-14 N23581 - May 14, 20:20 UTCMay 14, 21:15 UTC55m
2026-05-14 N23581 - May 14, 17:50 UTCMay 14, 18:55 UTC1h 5m
2026-05-13 N23581 - May 13, 21:55 UTCMay 13, 23:00 UTC1h 5m
2026-05-13 N23581 SEE → SEE May 13, 18:10 UTCMay 13, 19:00 UTC50m
2026-05-11 N23581 - May 11, 19:55 UTCMay 11, 21:00 UTC1h 5m
2026-05-11 N23581 SEE → SEE May 11, 18:15 UTCMay 11, 18:40 UTC25m
2026-05-10 N23581 - May 10, 19:54 UTCMay 10, 21:10 UTC1h 15m
2026-05-10 N23581 - May 10, 17:40 UTCMay 10, 18:55 UTC1h 15m
2026-05-10 N23581 - May 10, 00:30 UTCMay 10, 02:24 UTC1h 55m
2026-05-09 N23581 - May 9, 19:14 UTCMay 9, 21:09 UTC1h 55m
2026-05-08 N23581 - May 8, 20:00 UTCMay 8, 21:00 UTC1h 0m
2026-05-08 N23581 - May 8, 00:14 UTCMay 8, 01:00 UTC45m
2026-05-07 N23581 - May 7, 21:45 UTCMay 7, 22:50 UTC1h 5m
2026-05-07 N23581 SEE → SEE May 7, 18:05 UTCMay 7, 18:50 UTC45m
2026-05-06 N23581 - May 6, 22:00 UTCMay 6, 22:50 UTC50m
2026-05-06 N23581 SEE → SEE May 6, 18:05 UTCMay 6, 18:55 UTC50m
2026-05-04 N23581 SEE → SEE May 4, 17:55 UTCMay 4, 18:50 UTC56m
2026-05-01 N23581 - May 1, 22:30 UTCMay 1, 23:35 UTC1h 5m
2026-05-01 N23581 - May 1, 19:55 UTCMay 1, 20:50 UTC55m
2026-05-01 N23581 - May 1, 00:55 UTCMay 1, 01:35 UTC40m
2026-04-30 N23581 - Apr 30, 22:00 UTCApr 30, 22:55 UTC55m
2026-04-29 N23581 SEE → SEE Apr 29, 17:55 UTCApr 29, 18:25 UTC30m
2026-04-24 N23581 - Apr 24, 20:10 UTCApr 24, 20:35 UTC25m
2026-04-24 N23581 - Apr 24, 17:45 UTCApr 24, 18:50 UTC1h 5m
2026-04-23 N23581 - Apr 23, 22:05 UTCApr 23, 23:10 UTC1h 5m
2026-04-23 N23581 SEE → SEE Apr 23, 20:05 UTCApr 23, 21:05 UTC1h 0m
2026-04-23 N23581 SEE → SEE Apr 23, 17:50 UTCApr 23, 18:55 UTC1h 5m
2026-04-22 N23581 SEE → SEE Apr 22, 22:00 UTCApr 22, 22:35 UTC35m
2026-04-22 N23581 - Apr 22, 20:20 UTCApr 22, 21:05 UTC45m
2026-04-22 N23581 SEE → HMT Apr 22, 19:25 UTCApr 22, 20:10 UTC45m
2026-04-21 N23581 - Apr 21, 21:50 UTCApr 21, 22:50 UTC1h 0m
2026-04-21 N23581 SEE → SEE Apr 21, 20:00 UTCApr 21, 20:50 UTC50m
2026-04-19 N23581 SEE → SEE Apr 19, 18:35 UTCApr 19, 19:05 UTC30m
2026-04-17 N23581 - Apr 17, 17:40 UTCApr 17, 18:50 UTC1h 10m
2026-04-16 N23581 - Apr 16, 23:25 UTCApr 17, 00:30 UTC1h 5m
2026-04-16 N23581 - Apr 16, 20:05 UTCApr 16, 21:10 UTC1h 5m
2026-04-16 N23581 - Apr 16, 17:54 UTCApr 16, 18:50 UTC55m
2026-04-13 N23581 SEE → SEE Apr 13, 18:10 UTCApr 13, 18:45 UTC35m

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 N23581 page for operator, model, and routing details .

Mode-S A21E9D frequently asked

What is Mode-S code A21E9D?
A21E9D is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N23581.
Where is Mode-S A21E9D registered?
Mode-S code A21E9D 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 A21E9D broadcasting right now?
No active broadcast right now. Last signal was 13h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A21E9D, octal 50417235, decimal 10,624,669.
What flights does A21E9D operate?
Mode-S A21E9D has broadcast 1 distinct callsign, including N23581.