Apparatus

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sensors Mode-S transponder

A3999E

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N331AZ · BOEING 767-300 · operated by CARGO AIRCRAFT MANAGEMENT INC

Hex
A3999E
Octal
50714636
Decimal
10,721,694
Country
US
Tail
N331AZ
Type
B763
No current signal · last broadcast Jul 26, 21:00 UTC
Flights observed
168
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:00 UTC

Last known position

Most recent position reported by Mode-S A3999E.

Country allocation

The ICAO 24-bit address A3999E 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 20 distinct

Callsign Airline Flights Last seen
ATN3420 Air Transport International 4 2026-05-05
ATN3354 - 4 2026-07-12
ATN3341 Air Transport International 4 2026-07-26
ATN3310 Air Transport International 4 2026-07-23
ATN3376 - 3 2026-07-11
ATN3371 Air Transport International 3 2026-05-06
ATN3363 Air Transport International 3 2026-05-24
ATN3359 Air Transport International 3 2026-07-22
ATN3358 Air Transport International 3 2026-07-22
ATN3356 Air Transport International 3 2026-07-25
ATN3353 Air Transport International 3 2026-04-23
ATN3349 Air Transport International 3 2026-05-09
ATN3348 Air Transport International 3 2026-05-23
ATN3346 Air Transport International 3 2026-05-27
ATN3339 Air Transport International 3 2026-05-26
ATN3338 - 3 2026-07-09
ATN3333 Air Transport International 3 2026-05-05
ATN3327 Air Transport International 3 2026-07-26
ATN3319 Air Transport International 3 2026-05-19
ATN3304 Air Transport International 3 2026-05-20

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 ATN3327 SFO → ILN Jul 26, 19:00 UTCJul 26, 20:35 UTC1h 35m
2026-07-26 ATN3312 DEN → CVG Jul 26, 08:35 UTCJul 26, 10:10 UTC1h 35m
2026-07-26 ATN3341 BDL → CVG Jul 26, 04:00 UTCJul 26, 06:20 UTC2h 20m
2026-07-25 ATN3386 SBD → AUS Jul 25, 19:05 UTCJul 25, 21:15 UTC2h 10m
2026-07-25 ATN3356 CVG → BDL Jul 25, 02:00 UTCJul 25, 03:05 UTC1h 5m
2026-07-24 ATN3315 CVG → JFK Jul 24, 19:05 UTCJul 24, 20:55 UTC1h 50m
2026-07-24 ATN4302 CVG → MCI Jul 24, 13:10 UTCJul 24, 15:55 UTC2h 45m
2026-07-24 ATN4325 SBD → JFK Jul 24, 06:15 UTCJul 24, 09:15 UTC3h 0m
2026-07-23 ATN3310 SFO → CVG Jul 23, 19:55 UTCJul 23, 21:40 UTC1h 45m
2026-07-23 ATN6702 SFO → SBD Jul 23, 02:15 UTCJul 23, 03:10 UTC55m
2026-07-22 ATN3358 CVG → JFK Jul 22, 19:20 UTCJul 22, 20:25 UTC1h 5m
2026-07-22 ATN3359 ATL → CVG Jul 22, 11:10 UTCJul 22, 12:05 UTC55m
2026-07-21 ATN6767 CVG → RFD Jul 21, 01:00 UTCJul 21, 02:00 UTC1h 0m
2026-07-15 ATN3358 - Jul 15, 19:05 UTCJul 15, 20:05 UTC1h 0m
2026-07-14 ATN3359 JFK → CVG Jul 14, 10:30 UTCJul 14, 11:45 UTC1h 15m
2026-07-14 ATN3345 - Jul 14, 04:55 UTCJul 14, 06:15 UTC1h 20m
2026-07-13 ATN3343 - Jul 13, 19:35 UTCJul 13, 21:35 UTC2h 0m
2026-07-13 ATN3388 - Jul 13, 11:15 UTCJul 13, 14:05 UTC2h 50m
2026-07-13 ATN3330 - Jul 13, 04:45 UTCJul 13, 08:20 UTC3h 35m
2026-07-12 ATN3347 - Jul 12, 21:10 UTCJul 12, 22:20 UTC1h 10m
2026-07-12 ATN3354 - Jul 12, 16:40 UTCJul 12, 18:50 UTC2h 10m
2026-07-12 ATN3314 - Jul 12, 11:45 UTCJul 12, 13:20 UTC1h 35m
2026-07-12 ATN3350 - Jul 12, 04:30 UTCJul 12, 05:30 UTC1h 0m
2026-07-11 ATN3385 - Jul 11, 21:50 UTCJul 11, 23:30 UTC1h 40m
2026-07-11 ATN3376 - Jul 11, 17:20 UTCJul 11, 19:05 UTC1h 45m
2026-07-11 ATN3306 - Jul 11, 00:55 UTCJul 11, 03:10 UTC2h 15m
2026-07-10 ATN3327 - Jul 10, 18:50 UTCJul 10, 20:30 UTC1h 40m
2026-07-10 ATN3375 - Jul 10, 08:15 UTCJul 10, 09:10 UTC55m
2026-07-09 ATN3322 - Jul 9, 20:30 UTCJul 10, 00:35 UTC4h 5m
2026-07-09 ATN3338 - Jul 9, 12:30 UTCJul 9, 16:35 UTC4h 5m
2026-07-09 ATN6700 - Jul 9, 08:45 UTCJul 9, 10:00 UTC1h 15m
2026-07-07 ATN6731 - Jul 7, 02:10 UTCJul 7, 03:50 UTC1h 40m
2026-07-04 ATN4300 - Jul 4, 18:40 UTCJul 4, 19:45 UTC1h 5m
2026-07-04 ATN4314 CVG → BDL Jul 4, 08:20 UTCJul 4, 09:40 UTC1h 20m
2026-07-04 ATN4308 CVG → SCK Jul 4, 04:35 UTCJul 4, 05:35 UTC1h 0m
2026-07-03 ATN8331 - Jul 3, 13:30 UTCJul 3, 16:15 UTC2h 45m
2026-05-27 ATN3346 CVG → IAH May 27, 14:35 UTCMay 27, 18:40 UTC4h 5m
2026-05-27 ATN3300 AFW → SFO May 27, 06:15 UTCMay 27, 09:15 UTC3h 0m
2026-05-27 ATN3356 CVG → BDL May 27, 00:30 UTCMay 27, 02:59 UTC2h 30m
2026-05-26 ATN3339 IAH → CVG May 26, 18:55 UTCMay 26, 21:44 UTC2h 50m
2026-05-26 ATN4304 CVG → BDL May 26, 09:15 UTCMay 26, 11:24 UTC2h 10m
2026-05-26 ATN4355 CVG → MCI May 26, 05:00 UTCMay 26, 07:15 UTC2h 15m
2026-05-24 ATN3310 SFO → CVG May 24, 04:45 UTCMay 24, 07:45 UTC3h 0m
2026-05-24 ATN3363 JFK → RFD May 24, 00:15 UTCMay 24, 02:50 UTC2h 35m
2026-05-23 ATN3348 SFO → AFW May 23, 19:40 UTCMay 23, 21:50 UTC2h 10m
2026-05-23 ATN3321 AFW → PDX May 23, 12:25 UTCMay 23, 16:20 UTC3h 55m
2026-05-23 ATN3300 AFW → SFO May 23, 05:20 UTCMay 23, 08:50 UTC3h 30m
2026-05-23 ATN3356 CVG → BDL May 23, 00:25 UTCMay 23, 03:05 UTC2h 39m
2026-05-22 ATN3339 IAH → CVG May 22, 19:00 UTCMay 22, 21:30 UTC2h 30m
2026-05-22 ATN3310 SFO → CVG May 22, 05:05 UTCMay 22, 08:00 UTC2h 55m

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 N331AZ page for operator, model, and routing details .

Mode-S A3999E frequently asked

What is Mode-S code A3999E?
A3999E is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N331AZ.
Where is Mode-S A3999E registered?
Mode-S code A3999E 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 A3999E broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:00 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A3999E, octal 50714636, decimal 10,721,694.
What flights does A3999E operate?
Mode-S A3999E has broadcast 20 distinct callsigns, including ATN3420, ATN3354, ATN3341, ATN3310, ATN3376.