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sensors Mode-S transponder

A539B9

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N436DF · GRUMMAN S-2 Tracker · operated by USDA FOREST SERVICE - FEPP, CALIFORNIA DEPARTMENT OF FORESTRY AND FIRE, PROTECTION

Hex
A539B9
Octal
51234671
Decimal
10,828,217
Country
US
Tail
N436DF
Type
S2P
No current signal · last broadcast 1h ago
Flights observed
78
Distinct callsigns
1
Country
US
Last broadcast
1h ago

Last known position

Most recent position reported by Mode-S A539B9.

Country allocation

The ICAO 24-bit address A539B9 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
CFR76 - 78 2026-07-25

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-25 CFR76 - Jul 25, 23:50 UTCJul 26, 00:15 UTC25m
2026-07-25 CFR76 - Jul 25, 19:35 UTCJul 25, 19:45 UTC10m
2026-07-25 CFR76 - Jul 25, 15:45 UTCJul 25, 15:55 UTC10m
2026-07-25 CFR76 - Jul 25, 03:35 UTCJul 25, 03:45 UTC10m
2026-07-25 CFR76 - Jul 25, 01:30 UTCJul 25, 01:40 UTC10m
2026-07-24 CFR76 - Jul 24, 23:30 UTCJul 25, 00:25 UTC55m
2026-07-22 CFR76 - Jul 22, 23:30 UTCJul 23, 01:00 UTC1h 30m
2026-07-22 CFR76 - Jul 22, 20:40 UTCJul 22, 20:50 UTC10m
2026-07-22 CFR76 - Jul 22, 19:55 UTCJul 22, 20:05 UTC10m
2026-07-22 CFR76 - Jul 22, 17:25 UTCJul 22, 19:05 UTC1h 40m
2026-07-22 CFR76 - Jul 22, 16:25 UTCJul 22, 16:40 UTC15m
2026-07-22 CFR76 - Jul 22, 00:25 UTCJul 22, 01:35 UTC1h 10m
2026-07-21 CFR76 - Jul 21, 23:30 UTCJul 21, 23:40 UTC10m
2026-07-21 CFR76 - Jul 21, 19:30 UTCJul 21, 20:35 UTC1h 5m
2026-07-21 CFR76 - Jul 21, 17:15 UTCJul 21, 18:55 UTC1h 40m
2026-07-21 CFR76 - Jul 21, 15:35 UTCJul 21, 16:45 UTC1h 10m
2026-07-21 CFR76 - Jul 21, 01:45 UTCJul 21, 01:55 UTC10m
2026-07-21 CFR76 - Jul 21, 00:10 UTCJul 21, 01:15 UTC1h 5m
2026-07-18 CFR76 - Jul 18, 20:45 UTCJul 18, 22:40 UTC1h 55m
2026-07-17 CFR76 - Jul 17, 19:30 UTCJul 17, 19:49 UTC20m
2026-07-17 CFR76 - Jul 17, 02:25 UTCJul 17, 02:39 UTC15m
2026-07-17 CFR76 - Jul 17, 00:10 UTCJul 17, 01:29 UTC1h 20m
2026-07-16 CFR76 HMT → PTV Jul 16, 16:19 UTCJul 16, 17:05 UTC45m
2026-07-16 CFR76 - Jul 16, 02:00 UTCJul 16, 03:10 UTC1h 10m
2026-07-16 CFR76 - Jul 16, 00:15 UTCJul 16, 01:30 UTC1h 15m
2026-07-15 CFR76 - Jul 15, 18:45 UTCJul 15, 19:05 UTC20m
2026-07-14 CFR76 - Jul 14, 00:20 UTCJul 14, 01:05 UTC45m
2026-07-12 CFR76 - Jul 12, 23:20 UTCJul 13, 00:35 UTC1h 15m
2026-07-12 CFR76 - Jul 12, 19:25 UTCJul 12, 20:05 UTC40m
2026-07-12 CFR76 - Jul 12, 02:20 UTCJul 12, 02:40 UTC20m
2026-07-12 CFR76 - Jul 12, 00:50 UTCJul 12, 01:10 UTC20m
2026-07-11 CFR76 - Jul 11, 18:25 UTCJul 11, 20:20 UTC1h 55m
2026-07-11 CFR76 - Jul 11, 17:30 UTCJul 11, 17:40 UTC10m
2026-07-11 CFR76 - Jul 11, 01:55 UTCJul 11, 03:50 UTC1h 55m
2026-07-10 CFR76 - Jul 10, 22:00 UTCJul 10, 22:30 UTC30m
2026-07-09 CFR76 - Jul 9, 18:55 UTCJul 9, 20:00 UTC1h 5m
2026-07-08 CFR76 - Jul 8, 01:00 UTCJul 8, 01:50 UTC50m
2026-07-07 CFR76 - Jul 7, 22:35 UTCJul 8, 00:20 UTC1h 45m
2026-07-06 CFR76 - Jul 6, 23:40 UTCJul 7, 01:10 UTC1h 30m
2026-07-06 CFR76 - Jul 6, 18:15 UTCJul 6, 19:20 UTC1h 5m
2026-07-05 CFR76 - Jul 5, 21:35 UTCJul 5, 22:10 UTC35m
2026-07-04 CFR76 - Jul 4, 02:45 UTCJul 4, 03:25 UTC40m
2026-07-04 CFR76 - Jul 4, 01:50 UTCJul 4, 02:35 UTC45m
2026-07-02 CFR76 - Jul 2, 01:25 UTCJul 2, 03:25 UTC2h 0m
2026-07-01 CFR76 - Jul 1, 21:25 UTCJul 1, 21:40 UTC15m
2026-06-28 CFR76 - Jun 28, 22:29 UTCJun 28, 23:04 UTC35m
2026-06-27 CFR76 - Jun 27, 21:55 UTCJun 27, 23:14 UTC1h 20m
2026-06-25 CFR76 - Jun 25, 21:40 UTCJun 25, 22:10 UTC30m
2026-06-22 CFR76 - Jun 22, 01:15 UTCJun 22, 01:40 UTC25m
2026-06-21 CFR76 - Jun 21, 22:49 UTCJun 22, 00:04 UTC1h 15m

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 N436DF page for operator, model, and routing details .

Mode-S A539B9 frequently asked

What is Mode-S code A539B9?
A539B9 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N436DF.
Where is Mode-S A539B9 registered?
Mode-S code A539B9 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 A539B9 broadcasting right now?
No active broadcast right now. Last signal was 1h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A539B9, octal 51234671, decimal 10,828,217.
What flights does A539B9 operate?
Mode-S A539B9 has broadcast 1 distinct callsign, including CFR76.