Apparatus

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sensors Mode-S transponder

A2B1EF

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N273DC · DIAMOND DA-20 · operated by INDIANA STATE UNIVERSITY

Hex
A2B1EF
Octal
50530757
Decimal
10,662,383
Country
US
Tail
N273DC
Type
DV20
No current signal · last broadcast 1d ago
Flights observed
166
Distinct callsigns
1
Country
US
Last broadcast
1d ago

Last known position

Most recent position reported by Mode-S A2B1EF.

Country allocation

The ICAO 24-bit address A2B1EF 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
ISU5 - 166 2026-07-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-16 ISU5 HUF → HUF Jul 16, 15:30 UTCJul 16, 16:19 UTC50m
2026-07-16 ISU5 - Jul 16, 14:20 UTCJul 16, 14:45 UTC25m
2026-07-16 ISU5 - Jul 16, 13:25 UTCJul 16, 13:34 UTC10m
2026-07-16 ISU5 - Jul 16, 03:00 UTCJul 16, 03:40 UTC40m
2026-07-16 ISU5 HUF → HUF Jul 16, 00:55 UTCJul 16, 01:30 UTC35m
2026-07-15 ISU5 - Jul 15, 21:05 UTCJul 15, 21:40 UTC35m
2026-07-15 ISU5 - Jul 15, 17:05 UTCJul 15, 18:05 UTC1h 0m
2026-07-15 ISU5 - Jul 15, 14:50 UTCJul 15, 16:10 UTC1h 20m
2026-07-15 ISU5 - Jul 15, 12:15 UTCJul 15, 13:40 UTC1h 25m
2026-07-14 ISU5 - Jul 14, 23:50 UTCJul 15, 00:55 UTC1h 5m
2026-07-14 ISU5 VPZ → VPZ Jul 14, 21:00 UTCJul 14, 22:30 UTC1h 30m
2026-07-14 ISU5 - Jul 14, 13:10 UTCJul 14, 14:35 UTC1h 25m
2026-07-13 ISU5 - Jul 13, 22:55 UTCJul 13, 23:10 UTC15m
2026-07-13 ISU5 HUF → HUF Jul 13, 20:35 UTCJul 13, 21:40 UTC1h 5m
2026-07-13 ISU5 - Jul 13, 18:00 UTCJul 13, 18:10 UTC10m
2026-07-13 ISU5 - Jul 13, 17:05 UTCJul 13, 17:20 UTC15m
2026-07-13 ISU5 - Jul 13, 15:40 UTCJul 13, 16:10 UTC30m
2026-07-13 ISU5 - Jul 13, 13:20 UTCJul 13, 14:40 UTC1h 20m
2026-07-13 ISU5 - Jul 13, 12:20 UTCJul 13, 12:40 UTC20m
2026-07-13 ISU5 - Jul 13, 11:25 UTCJul 13, 11:45 UTC20m
2026-07-12 ISU5 HUF → HUF Jul 12, 16:45 UTCJul 12, 17:10 UTC25m
2026-07-11 ISU5 - Jul 11, 19:35 UTCJul 11, 20:20 UTC45m
2026-07-11 ISU5 - Jul 11, 14:20 UTCJul 11, 15:15 UTC55m
2026-07-11 ISU5 HUF → VPZ Jul 11, 10:45 UTCJul 11, 12:00 UTC1h 15m
2026-07-10 ISU5 - Jul 10, 21:30 UTCJul 10, 22:35 UTC1h 5m
2026-07-08 ISU5 - Jul 8, 21:30 UTCJul 8, 22:50 UTC1h 20m
2026-07-08 ISU5 - Jul 8, 19:25 UTCJul 8, 20:45 UTC1h 20m
2026-07-08 ISU5 - Jul 8, 13:15 UTCJul 8, 14:35 UTC1h 20m
2026-07-08 ISU5 - Jul 8, 11:25 UTCJul 8, 12:00 UTC35m
2026-07-08 ISU5 - Jul 8, 04:35 UTCJul 8, 04:55 UTC20m
2026-07-08 ISU5 - Jul 8, 03:50 UTCJul 8, 04:00 UTC10m
2026-07-07 ISU5 - Jul 7, 16:55 UTCJul 7, 17:45 UTC50m
2026-07-07 ISU5 - Jul 7, 13:55 UTCJul 7, 14:45 UTC50m
2026-07-07 ISU5 - Jul 7, 11:35 UTCJul 7, 11:45 UTC10m
2026-07-06 ISU5 - Jul 6, 21:00 UTCJul 6, 22:05 UTC1h 5m
2026-07-03 ISU5 - Jul 3, 01:15 UTCJul 3, 01:35 UTC20m
2026-07-02 ISU5 - Jul 2, 03:05 UTCJul 2, 05:05 UTC2h 0m
2026-07-02 ISU5 - Jul 2, 01:25 UTCJul 2, 02:25 UTC1h 0m
2026-07-01 ISU5 - Jul 1, 13:20 UTCJul 1, 13:30 UTC10m
2026-07-01 ISU5 - Jul 1, 11:40 UTCJul 1, 12:20 UTC40m
2026-06-29 ISU5 HUF → HUF Jun 29, 13:49 UTCJun 29, 13:59 UTC10m
2026-06-18 ISU5 - Jun 18, 19:00 UTCJun 18, 19:35 UTC35m
2026-06-18 ISU5 - Jun 18, 13:30 UTCJun 18, 13:40 UTC10m
2026-06-18 ISU5 - Jun 18, 11:05 UTCJun 18, 12:25 UTC1h 20m
2026-06-17 ISU5 - Jun 17, 13:35 UTCJun 17, 14:50 UTC1h 15m
2026-06-16 ISU5 - Jun 16, 20:50 UTCJun 16, 21:55 UTC1h 5m
2026-06-16 ISU5 - Jun 16, 13:34 UTCJun 16, 13:44 UTC10m
2026-06-15 ISU5 HUF → HUF Jun 15, 21:04 UTCJun 15, 22:30 UTC1h 25m
2026-06-15 ISU5 - Jun 15, 16:49 UTCJun 15, 17:04 UTC15m
2026-06-15 ISU5 - Jun 15, 14:55 UTCJun 15, 15:10 UTC15m

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 N273DC page for operator, model, and routing details .

Mode-S A2B1EF frequently asked

What is Mode-S code A2B1EF?
A2B1EF is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N273DC.
Where is Mode-S A2B1EF registered?
Mode-S code A2B1EF 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 A2B1EF broadcasting right now?
No active broadcast right now. Last signal was 1d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A2B1EF, octal 50530757, decimal 10,662,383.
What flights does A2B1EF operate?
Mode-S A2B1EF has broadcast 1 distinct callsign, including ISU5.