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 Jul 26, 20:20 UTC
Flights observed
281
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:20 UTC

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 Cape Air 32 2026-07-19
KAP6789 Cape Air 13 2026-05-18
KAP33 - 12 2026-07-16
KAP516 Cape Air 11 2026-05-29
KAP87 Cape Air 10 2026-07-23
KAP419 - 9 2026-07-14
KAP426 Cape Air 8 2026-06-03
KAP328 Cape Air 7 2026-07-25
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
KAP3241 Cape Air 5 2026-07-19
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

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 KAP394 HYA → MYR Jul 26, 19:00 UTCJul 26, 20:20 UTC1h 20m
2026-07-26 KAP394 HYA → MYR Jul 26, 16:55 UTCJul 26, 17:50 UTC55m
2026-07-25 KAP328 BOS → BHB Jul 25, 01:55 UTCJul 25, 02:05 UTC10m
2026-07-25 KAP328 BOS → BHB Jul 25, 00:45 UTCJul 25, 01:15 UTC30m
2026-07-24 KAP7581 ACK → HYA Jul 24, 22:55 UTCJul 24, 23:35 UTC40m
2026-07-24 KAP328 BOS → BHB Jul 24, 21:20 UTCJul 24, 21:50 UTC30m
2026-07-24 KAP5261 ACK → BOS Jul 24, 19:45 UTCJul 24, 20:15 UTC30m
2026-07-24 KAP328 BOS → BHB Jul 24, 18:30 UTCJul 24, 19:00 UTC30m
2026-07-24 KAP7021 HYA → BOS Jul 24, 17:20 UTCJul 24, 17:45 UTC25m
2026-07-23 KAP87 STT → STX Jul 23, 21:15 UTCJul 23, 21:50 UTC35m
2026-07-23 KAP5061 ACK → BOS Jul 23, 19:40 UTCJul 23, 20:10 UTC30m
2026-07-23 KAP87 STT → STX Jul 23, 17:45 UTCJul 23, 18:15 UTC30m
2026-07-23 KAP5081 ACK → BOS Jul 23, 16:20 UTCJul 23, 17:05 UTC45m
2026-07-23 KAP87 STT → STX Jul 23, 14:40 UTCJul 23, 15:15 UTC35m
2026-07-23 KAP5041 ACK → BOS Jul 23, 13:00 UTCJul 23, 13:40 UTC40m
2026-07-22 KAP519 BOS → ALB Jul 22, 22:20 UTCJul 22, 23:30 UTC1h 10m
2026-07-22 KAP519 BOS → ALB Jul 22, 19:30 UTCJul 22, 20:15 UTC45m
2026-07-22 KAP519 BOS → ALB Jul 22, 18:20 UTCJul 22, 18:50 UTC30m
2026-07-22 KAP924 STL → TBN Jul 22, 16:25 UTCJul 22, 16:45 UTC20m
2026-07-19 KAP527 BOS → BHB Jul 19, 17:30 UTCJul 19, 17:55 UTC25m
2026-07-19 KAP3241 MVY → BOS Jul 19, 15:55 UTCJul 19, 16:35 UTC40m
2026-07-19 KAP527 BOS → BHB Jul 19, 14:10 UTCJul 19, 14:30 UTC20m
2026-07-19 KAP3221 MVY → BOS Jul 19, 12:45 UTCJul 19, 13:20 UTC35m
2026-07-19 KAP527 BOS → BHB Jul 19, 11:05 UTCJul 19, 11:20 UTC15m
2026-07-18 KAP527 - Jul 18, 19:00 UTCJul 18, 19:25 UTC25m
2026-07-18 KAP527 - Jul 18, 17:20 UTCJul 18, 18:25 UTC1h 5m
2026-07-18 KAP3241 MVY → BOS Jul 18, 15:55 UTCJul 18, 16:35 UTC40m
2026-07-18 KAP527 - Jul 18, 14:15 UTCJul 18, 14:45 UTC30m
2026-07-18 KAP3221 - Jul 18, 12:55 UTCJul 18, 13:40 UTC45m
2026-07-18 KAP527 - Jul 18, 10:50 UTCJul 18, 11:10 UTC20m
2026-07-17 KAP527 - Jul 17, 19:25 UTCJul 17, 19:40 UTC15m
2026-07-17 KAP527 - Jul 17, 17:15 UTCJul 17, 18:05 UTC50m
2026-07-17 KAP3241 - Jul 17, 16:00 UTCJul 17, 16:29 UTC30m
2026-07-17 KAP527 BOS → MVY Jul 17, 14:04 UTCJul 17, 14:24 UTC20m
2026-07-17 KAP3221 - Jul 17, 12:50 UTCJul 17, 13:29 UTC40m
2026-07-17 KAP527 - Jul 17, 11:20 UTCJul 17, 11:39 UTC20m
2026-07-16 KAP33 BOS → EWB Jul 16, 17:25 UTCJul 16, 18:15 UTC50m
2026-07-16 KAP33 - Jul 16, 16:05 UTCJul 16, 16:30 UTC25m
2026-07-16 KAP33 BOS → MVY Jul 16, 14:20 UTCJul 16, 14:45 UTC25m
2026-07-16 KAP33 - Jul 16, 12:40 UTCJul 16, 13:05 UTC25m
2026-07-16 KAP33 - Jul 16, 11:10 UTCJul 16, 12:05 UTC55m
2026-07-15 KAP33 BOS → EWB Jul 15, 19:10 UTCJul 15, 20:05 UTC55m
2026-07-15 KAP33 - Jul 15, 17:50 UTCJul 15, 18:15 UTC25m
2026-07-15 KAP33 - Jul 15, 15:45 UTCJul 15, 16:05 UTC20m
2026-07-15 KAP33 - Jul 15, 14:35 UTCJul 15, 15:05 UTC30m
2026-07-15 KAP33 BOS → MVY Jul 15, 12:55 UTCJul 15, 13:15 UTC20m
2026-07-15 KAP33 - Jul 15, 11:40 UTCJul 15, 12:10 UTC30m
2026-07-15 KAP33 - Jul 15, 10:50 UTCJul 15, 11:00 UTC10m
2026-07-14 KAP419 - Jul 14, 20:05 UTCJul 14, 20:15 UTC10m
2026-07-14 KAP419 - Jul 14, 19:00 UTCJul 14, 19:25 UTC25m

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 Jul 26, 20:20 UTC.
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, KAP33, KAP516, KAP87.