Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A09AAF

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N138UD · CESSNA 172 Skyhawk · operated by ALF IX LLC

Hex
A09AAF
Octal
50115257
Decimal
10,525,359
Country
US
Tail
N138UD
Type
C172
No current signal · last broadcast 7h ago
Flights observed
170
Distinct callsigns
1
Country
US
Last broadcast
7h ago

Last known position

Most recent position reported by Mode-S A09AAF.

Country allocation

The ICAO 24-bit address A09AAF 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
N138UD - 170 2026-07-14

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 N138UD - Jul 14, 00:25 UTCJul 14, 00:35 UTC10m
2026-07-13 N138UD - Jul 13, 23:55 UTCJul 14, 00:20 UTC25m
2026-07-13 N138UD - Jul 13, 18:55 UTCJul 13, 20:35 UTC1h 40m
2026-07-13 N138UD - Jul 13, 15:50 UTCJul 13, 16:45 UTC55m
2026-07-13 N138UD - Jul 13, 12:20 UTCJul 13, 14:20 UTC2h 0m
2026-07-13 N138UD - Jul 13, 11:50 UTCJul 13, 12:15 UTC25m
2026-07-10 N138UD - Jul 10, 15:50 UTCJul 10, 16:25 UTC35m
2026-07-10 N138UD - Jul 10, 13:40 UTCJul 10, 14:30 UTC50m
2026-07-10 N138UD - Jul 10, 11:35 UTCJul 10, 12:30 UTC55m
2026-07-09 N138UD - Jul 9, 16:05 UTCJul 9, 16:45 UTC40m
2026-07-09 N138UD - Jul 9, 12:35 UTCJul 9, 13:40 UTC1h 5m
2026-07-02 N138UD - Jul 2, 13:20 UTCJul 2, 15:45 UTC2h 25m
2026-07-02 N138UD - Jul 2, 01:30 UTCJul 2, 03:45 UTC2h 15m
2026-07-01 N138UD - Jul 1, 15:35 UTCJul 1, 16:35 UTC1h 0m
2026-07-01 N138UD SBY → SBY Jul 1, 13:40 UTCJul 1, 14:20 UTC40m
2026-07-01 N138UD - Jul 1, 11:30 UTCJul 1, 11:40 UTC10m
2026-06-30 N138UD - Jun 30, 17:55 UTCJun 30, 18:50 UTC55m
2026-06-30 N138UD - Jun 30, 16:40 UTCJun 30, 17:00 UTC20m
2026-06-30 N138UD - Jun 30, 15:40 UTCJun 30, 16:35 UTC55m
2026-06-30 N138UD - Jun 30, 13:40 UTCJun 30, 14:25 UTC45m
2026-06-26 N138UD - Jun 26, 18:44 UTCJun 26, 19:24 UTC40m
2026-06-26 N138UD - Jun 26, 17:59 UTCJun 26, 18:34 UTC35m
2026-06-26 N138UD - Jun 26, 16:00 UTCJun 26, 16:35 UTC35m
2026-06-26 N138UD - Jun 26, 13:45 UTCJun 26, 14:39 UTC55m
2026-06-25 N138UD - Jun 25, 18:50 UTCJun 25, 19:34 UTC45m
2026-06-25 N138UD - Jun 25, 11:54 UTCJun 25, 12:25 UTC30m
2026-06-25 N138UD - Jun 25, 01:24 UTCJun 25, 02:14 UTC50m
2026-06-24 N138UD - Jun 24, 15:54 UTCJun 24, 16:45 UTC50m
2026-06-24 N138UD - Jun 24, 13:50 UTCJun 24, 15:00 UTC1h 10m
2026-06-22 N138UD - Jun 22, 15:54 UTCJun 22, 16:45 UTC50m
2026-06-22 N138UD - Jun 22, 13:44 UTCJun 22, 14:40 UTC55m
2026-06-22 N138UD - Jun 22, 11:50 UTCJun 22, 12:30 UTC40m
2026-06-18 N138UD - Jun 18, 01:30 UTCJun 18, 02:00 UTC30m
2026-06-17 N138UD - Jun 17, 22:20 UTCJun 17, 23:40 UTC1h 20m
2026-06-17 N138UD - Jun 17, 18:20 UTCJun 17, 19:00 UTC40m
2026-06-17 N138UD - Jun 17, 13:10 UTCJun 17, 13:30 UTC20m
2026-06-16 N138UD - Jun 16, 20:30 UTCJun 16, 21:40 UTC1h 10m
2026-06-16 N138UD - Jun 16, 16:05 UTCJun 16, 17:30 UTC1h 25m
2026-06-16 N138UD - Jun 16, 14:09 UTCJun 16, 14:20 UTC10m
2026-06-16 N138UD - Jun 16, 13:25 UTCJun 16, 13:44 UTC20m
2026-06-15 N138UD - Jun 15, 15:55 UTCJun 15, 16:40 UTC45m
2026-06-15 N138UD - Jun 15, 12:00 UTCJun 15, 12:49 UTC50m
2026-06-12 N138UD SBY → SBY Jun 12, 15:40 UTCJun 12, 16:35 UTC55m
2026-06-12 N138UD - Jun 12, 13:25 UTCJun 12, 13:55 UTC30m
2026-06-12 N138UD - Jun 12, 11:30 UTCJun 12, 12:30 UTC1h 0m
2026-06-11 N138UD - Jun 11, 16:15 UTCJun 11, 16:55 UTC40m
2026-06-11 N138UD - Jun 11, 13:30 UTCJun 11, 14:40 UTC1h 10m
2026-06-09 N138UD - Jun 9, 19:15 UTCJun 9, 20:45 UTC1h 30m
2026-06-09 N138UD - Jun 9, 16:45 UTCJun 9, 17:55 UTC1h 10m
2026-06-09 N138UD - Jun 9, 14:15 UTCJun 9, 14:55 UTC40m

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 N138UD page for operator, model, and routing details .

Mode-S A09AAF frequently asked

What is Mode-S code A09AAF?
A09AAF is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N138UD.
Where is Mode-S A09AAF registered?
Mode-S code A09AAF 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 A09AAF broadcasting right now?
No active broadcast right now. Last signal was 7h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A09AAF, octal 50115257, decimal 10,525,359.
What flights does A09AAF operate?
Mode-S A09AAF has broadcast 1 distinct callsign, including N138UD.