Apparatus

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sensors Mode-S transponder

ADF43E

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N999BU · VANS RV-6 · operated by UTAH FIREFLY LLC

Hex
ADF43E
Octal
53372076
Decimal
11,400,254
Country
US
Tail
N999BU
Type
RV6
No current signal · last broadcast 3d ago
Flights observed
66
Distinct callsigns
1
Country
US
Last broadcast
3d ago

Last known position

Most recent position reported by Mode-S ADF43E.

Country allocation

The ICAO 24-bit address ADF43E 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
N999BU - 66 2026-07-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-22 N999BU - Jul 22, 17:45 UTCJul 22, 18:25 UTC40m
2026-07-22 N999BU ESD → RNT Jul 22, 16:10 UTCJul 22, 16:55 UTC45m
2026-07-18 N999BU - Jul 18, 22:30 UTCJul 18, 23:05 UTC35m
2026-07-17 N999BU - Jul 17, 22:49 UTCJul 17, 23:05 UTC15m
2026-07-16 N999BU - Jul 16, 00:10 UTCJul 16, 01:35 UTC1h 25m
2026-07-12 N999BU ESD → ESD Jul 12, 17:20 UTCJul 12, 17:45 UTC25m
2026-07-11 N999BU - Jul 11, 17:00 UTCJul 11, 18:10 UTC1h 10m
2026-07-11 N999BU RSJ → TWD Jul 11, 15:05 UTCJul 11, 15:25 UTC20m
2026-07-11 N999BU - Jul 11, 01:05 UTCJul 11, 01:55 UTC50m
2026-07-09 N999BU - Jul 9, 23:05 UTCJul 9, 23:15 UTC10m
2026-07-09 N999BU - Jul 9, 19:40 UTCJul 9, 19:55 UTC15m
2026-07-09 N999BU - Jul 9, 01:40 UTCJul 9, 03:05 UTC1h 25m
2026-06-28 N999BU ESD → ESD Jun 28, 22:10 UTCJun 28, 22:29 UTC20m
2026-06-24 N999BU - Jun 24, 16:24 UTCJun 24, 16:34 UTC10m
2026-06-23 N999BU ESD → ESD Jun 23, 18:45 UTCJun 23, 18:55 UTC10m
2026-06-15 N999BU - Jun 15, 03:05 UTCJun 15, 03:30 UTC25m
2026-06-14 N999BU - Jun 14, 23:05 UTCJun 14, 23:29 UTC24m
2026-06-11 N999BU - Jun 11, 19:15 UTCJun 11, 19:25 UTC10m
2026-06-11 N999BU - Jun 11, 16:20 UTCJun 11, 16:30 UTC10m
2026-06-08 N999BU - Jun 8, 18:25 UTCJun 8, 19:15 UTC50m
2026-06-08 N999BU - Jun 8, 17:45 UTCJun 8, 17:55 UTC10m
2026-06-08 N999BU - Jun 8, 15:40 UTCJun 8, 16:05 UTC25m
2026-06-08 N999BU - Jun 8, 13:55 UTCJun 8, 14:45 UTC50m
2026-06-08 N999BU - Jun 8, 13:00 UTCJun 8, 13:10 UTC10m
2026-06-03 N999BU - Jun 3, 21:40 UTCJun 3, 21:50 UTC10m
2026-06-03 N999BU - Jun 3, 20:10 UTCJun 3, 21:05 UTC55m
2026-06-03 N999BU - Jun 3, 18:55 UTCJun 3, 19:15 UTC20m
2026-06-03 N999BU - Jun 3, 15:25 UTCJun 3, 16:20 UTC55m
2026-05-30 N999BU - May 30, 21:55 UTCMay 30, 22:05 UTC10m
2026-05-30 N999BU - May 30, 20:20 UTCMay 30, 20:30 UTC10m
2026-05-24 N999BU - May 24, 23:00 UTCMay 24, 23:46 UTC46m
2026-05-24 N999BU - May 24, 19:50 UTCMay 24, 21:45 UTC1h 55m
2026-05-22 N999BU MFR → STS May 22, 01:50 UTCMay 22, 03:30 UTC1h 40m
2026-05-21 N999BU - May 21, 22:15 UTCMay 22, 00:55 UTC2h 40m
2026-05-20 N999BU ESD → ESD May 20, 17:40 UTCMay 20, 18:30 UTC50m
2026-05-20 N999BU - May 20, 02:30 UTCMay 20, 02:45 UTC15m
2026-05-19 N999BU RSJ → MVW May 19, 23:30 UTCMay 19, 23:45 UTC15m
2026-05-17 N999BU ESD → ESD May 17, 17:55 UTCMay 17, 18:15 UTC20m
2026-05-17 N999BU ESD → ESD May 17, 01:40 UTCMay 17, 02:40 UTC1h 0m
2026-05-12 N999BU - May 12, 18:05 UTCMay 12, 18:35 UTC30m
2026-05-11 N999BU - May 11, 19:40 UTCMay 11, 20:15 UTC35m
2026-05-10 N999BU ESD → ESD May 10, 20:35 UTCMay 10, 21:14 UTC40m
2026-05-09 N999BU ESD → ESD May 9, 20:44 UTCMay 9, 21:09 UTC25m
2026-05-09 N999BU - May 9, 18:40 UTCMay 9, 18:55 UTC15m
2026-05-09 N999BU - May 9, 16:50 UTCMay 9, 17:15 UTC25m
2026-05-07 N999BU - May 7, 19:15 UTCMay 7, 20:10 UTC55m
2026-05-07 N999BU ESD → FRD May 7, 16:45 UTCMay 7, 17:45 UTC1h 0m
2026-05-04 N999BU - May 4, 21:55 UTCMay 4, 22:05 UTC10m
2026-05-04 N999BU - May 4, 18:35 UTCMay 4, 18:45 UTC10m
2026-05-03 N999BU ESD → ESD May 3, 21:00 UTCMay 3, 21:20 UTC20m

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 N999BU page for operator, model, and routing details .

Mode-S ADF43E frequently asked

What is Mode-S code ADF43E?
ADF43E is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N999BU.
Where is Mode-S ADF43E registered?
Mode-S code ADF43E 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 ADF43E broadcasting right now?
No active broadcast right now. Last signal was 3d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex ADF43E, octal 53372076, decimal 11,400,254.
What flights does ADF43E operate?
Mode-S ADF43E has broadcast 1 distinct callsign, including N999BU.