Apparatus

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sensors Mode-S transponder

A4B1FE

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N401SX · CESSNA 402 Businessliner · operated by HYANNIS AIR SERVICE INC

Hex
A4B1FE
Octal
51130776
Decimal
10,793,470
Country
US
Tail
N401SX
Type
C402
No current signal · last broadcast 13h ago
Flights observed
226
Distinct callsigns
20
Country
US
Last broadcast
13h ago

Last known position

Most recent position reported by Mode-S A4B1FE.

Country allocation

The ICAO 24-bit address A4B1FE 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
KAP527 - 21 2026-07-12
KAP6789 Cape Air 13 2026-05-18
KAP516 Cape Air 11 2026-05-29
KAP426 Cape Air 8 2026-06-03
KAP87 - 7 2026-07-03
KAP321 Cape Air 7 2026-05-31
KAP212 Cape Air 7 2026-05-02
KAP413 Cape Air 6 2026-04-13
KAP1838 Cape Air 6 2026-05-02
KAP925 - 5 2026-06-27
KAP5241 Cape Air 5 2026-05-23
KAP3064 Cape Air 5 2026-04-24
KAP845 Cape Air 4 2026-04-30
KAP5573 Cape Air 4 2026-05-13
KAP5221 Cape Air 4 2026-05-23
KAP333 Cape Air 4 2026-05-14
KAP210 Cape Air 4 2026-05-20
KAP155 - 4 2026-06-30
KAP1034 - 4 2026-06-28
KAP1026 Cape Air 4 2026-06-28

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 KAP419 BOS → EWB Jul 13, 19:25 UTCJul 13, 20:25 UTC1h 0m
2026-07-13 KAP3161 - Jul 13, 17:55 UTCJul 13, 18:35 UTC40m
2026-07-13 KAP419 - Jul 13, 16:00 UTCJul 13, 16:25 UTC25m
2026-07-13 KAP3001 - Jul 13, 14:35 UTCJul 13, 15:10 UTC35m
2026-07-13 KAP419 - Jul 13, 12:55 UTCJul 13, 13:20 UTC25m
2026-07-13 KAP3101 - Jul 13, 10:55 UTCJul 13, 12:10 UTC1h 15m
2026-07-12 KAP527 - Jul 12, 19:35 UTCJul 12, 19:55 UTC20m
2026-07-12 KAP527 - Jul 12, 18:35 UTCJul 12, 18:45 UTC10m
2026-07-12 KAP527 - Jul 12, 17:20 UTCJul 12, 17:45 UTC25m
2026-07-12 KAP3241 - Jul 12, 16:01 UTCJul 12, 16:30 UTC30m
2026-07-12 KAP527 - Jul 12, 14:10 UTCJul 12, 14:35 UTC25m
2026-07-12 KAP3221 - Jul 12, 12:45 UTCJul 12, 13:20 UTC35m
2026-07-12 KAP527 - Jul 12, 11:55 UTCJul 12, 12:05 UTC10m
2026-07-12 KAP527 - Jul 12, 11:05 UTCJul 12, 11:25 UTC20m
2026-07-12 KAP3291 - Jul 12, 00:01 UTCJul 12, 00:45 UTC45m
2026-07-11 KAP3061 - Jul 11, 22:20 UTCJul 11, 22:50 UTC30m
2026-07-11 KAP3171 - Jul 11, 20:45 UTCJul 11, 21:10 UTC25m
2026-07-11 KAP3081 - Jul 11, 19:10 UTCJul 11, 19:35 UTC25m
2026-07-11 KAP3252 - Jul 11, 17:50 UTCJul 11, 18:20 UTC30m
2026-07-11 KAP3242 MVY → BOS Jul 11, 16:15 UTCJul 11, 16:55 UTC40m
2026-07-11 KAP1022 - Jul 11, 15:25 UTCJul 11, 15:35 UTC10m
2026-07-04 KAP548 - Jul 4, 17:55 UTCJul 4, 18:10 UTC15m
2026-07-03 KAP87 - Jul 3, 21:40 UTCJul 3, 21:50 UTC10m
2026-07-03 KAP87 - Jul 3, 20:15 UTCJul 3, 20:50 UTC35m
2026-07-03 KAP87 - Jul 3, 18:40 UTCJul 3, 19:05 UTC25m
2026-07-03 KAP87 - Jul 3, 16:45 UTCJul 3, 16:55 UTC10m
2026-07-03 KAP87 - Jul 3, 15:05 UTCJul 3, 16:05 UTC1h 0m
2026-07-03 KAP87 - Jul 3, 12:55 UTCJul 3, 13:55 UTC1h 0m
2026-07-03 KAP87 - Jul 3, 11:20 UTCJul 3, 11:30 UTC10m
2026-07-03 KAP328 - Jul 3, 02:20 UTCJul 3, 02:45 UTC25m
2026-07-03 KAP6107 - Jul 3, 00:50 UTCJul 3, 01:25 UTC35m
2026-07-02 KAP328 - Jul 2, 23:15 UTCJul 2, 23:55 UTC40m
2026-07-02 KAP5201 - Jul 2, 21:20 UTCJul 2, 22:05 UTC45m
2026-07-02 KAP328 - Jul 2, 19:25 UTCJul 2, 20:05 UTC40m
2026-07-02 KAP7001 - Jul 2, 18:00 UTCJul 2, 18:20 UTC20m
2026-07-01 KAPT747 - Jul 1, 12:45 UTCJul 1, 14:20 UTC1h 35m
2026-06-30 KAPT106 - Jun 30, 17:20 UTCJun 30, 18:50 UTC1h 30m
2026-06-30 KAP155 - Jun 30, 02:25 UTCJun 30, 02:40 UTC15m
2026-06-30 KAP155 BOS → MVY Jun 30, 01:14 UTCJun 30, 01:40 UTC26m
2026-06-29 KAP3321 MVY → BOS Jun 29, 23:49 UTCJun 30, 00:20 UTC30m
2026-06-29 KAP452 - Jun 29, 22:39 UTCJun 29, 23:05 UTC25m
2026-06-29 KAP452 - Jun 29, 20:49 UTCJun 29, 21:24 UTC35m
2026-06-29 KAP155 - Jun 29, 19:35 UTCJun 29, 20:00 UTC25m
2026-06-29 KAP7161 HYA → BOS Jun 29, 18:25 UTCJun 29, 18:55 UTC30m
2026-06-28 KAP811 - Jun 28, 21:20 UTCJun 28, 21:40 UTC20m
2026-06-28 KAP1034 - Jun 28, 19:14 UTCJun 28, 20:50 UTC1h 35m
2026-06-28 KAP501 - Jun 28, 16:39 UTCJun 28, 17:44 UTC1h 5m
2026-06-28 KAP1026 SLK → BOS Jun 28, 14:39 UTCJun 28, 15:55 UTC1h 15m
2026-06-28 KAP811 - Jun 28, 11:55 UTCJun 28, 13:29 UTC1h 35m
2026-06-27 KAP925 - Jun 27, 17:04 UTCJun 27, 17:39 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 N401SX page for operator, model, and routing details .

Mode-S A4B1FE frequently asked

What is Mode-S code A4B1FE?
A4B1FE is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N401SX.
Where is Mode-S A4B1FE registered?
Mode-S code A4B1FE 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 A4B1FE 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 A4B1FE, octal 51130776, decimal 10,793,470.
What flights does A4B1FE operate?
Mode-S A4B1FE has broadcast 20 distinct callsigns, including KAP527, KAP6789, KAP516, KAP426, KAP87.