Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A51A87

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N428ND · operated by UNIVERSITY OF NORTH DAKOTA

Hex
A51A87
Octal
51215207
Decimal
10,820,231
Country
US
Tail
N428ND
No current signal · last broadcast 20h ago
Flights observed
83
Distinct callsigns
2
Country
US
Last broadcast
20h ago

Last known position

Most recent position reported by Mode-S A51A87.

Country allocation

The ICAO 24-bit address A51A87 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 2 distinct

Callsign Airline Flights Last seen
NDU28 - 69 2026-07-13
N428ND - 14 2026-05-03

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 NDU28 - Jul 13, 14:25 UTCJul 13, 14:40 UTC15m
2026-07-11 NDU28 - Jul 11, 20:30 UTCJul 11, 21:15 UTC45m
2026-07-11 NDU28 - Jul 11, 17:45 UTCJul 11, 18:40 UTC55m
2026-07-11 NDU28 - Jul 11, 15:25 UTCJul 11, 16:45 UTC1h 20m
2026-07-11 NDU28 - Jul 11, 12:55 UTCJul 11, 13:20 UTC25m
2026-07-10 NDU28 - Jul 10, 21:25 UTCJul 10, 22:20 UTC55m
2026-07-10 NDU28 - Jul 10, 17:15 UTCJul 10, 18:25 UTC1h 10m
2026-07-10 NDU28 - Jul 10, 15:50 UTCJul 10, 16:00 UTC10m
2026-07-10 NDU28 - Jul 10, 13:40 UTCJul 10, 13:50 UTC10m
2026-07-09 NDU28 - Jul 9, 20:35 UTCJul 9, 21:15 UTC40m
2026-07-09 NDU28 - Jul 9, 19:10 UTCJul 9, 19:25 UTC15m
2026-07-09 NDU28 - Jul 9, 12:25 UTCJul 9, 13:30 UTC1h 5m
2026-07-09 NDU28 - Jul 9, 00:20 UTCJul 9, 00:40 UTC20m
2026-07-08 NDU28 - Jul 8, 19:55 UTCJul 8, 20:50 UTC55m
2026-07-07 NDU28 - Jul 7, 17:30 UTCJul 7, 17:45 UTC15m
2026-07-07 NDU28 - Jul 7, 15:05 UTCJul 7, 15:35 UTC30m
2026-07-01 NDU28 - Jul 1, 21:35 UTCJul 1, 21:45 UTC10m
2026-07-01 NDU28 - Jul 1, 13:20 UTCJul 1, 14:45 UTC1h 25m
2026-06-27 NDU28 - Jun 27, 02:59 UTCJun 27, 03:44 UTC45m
2026-06-27 NDU28 - Jun 27, 01:15 UTCJun 27, 01:49 UTC35m
2026-06-26 NDU28 - Jun 26, 21:59 UTCJun 26, 22:34 UTC35m
2026-06-26 NDU28 - Jun 26, 14:05 UTCJun 26, 14:59 UTC55m
2026-06-26 NDU28 - Jun 26, 01:20 UTCJun 26, 01:29 UTC10m
2026-06-23 NDU28 - Jun 23, 01:35 UTCJun 23, 02:04 UTC30m
2026-06-22 NDU28 - Jun 22, 12:30 UTCJun 22, 13:19 UTC50m
2026-06-20 NDU28 - Jun 20, 18:14 UTCJun 20, 18:49 UTC35m
2026-06-20 NDU28 - Jun 20, 17:04 UTCJun 20, 17:24 UTC20m
2026-06-18 NDU28 - Jun 18, 20:25 UTCJun 18, 20:35 UTC10m
2026-06-18 NDU28 - Jun 18, 00:45 UTCJun 18, 01:05 UTC20m
2026-06-17 NDU28 - Jun 17, 18:20 UTCJun 17, 19:20 UTC1h 0m
2026-06-16 NDU28 - Jun 16, 14:25 UTCJun 16, 15:24 UTC1h 0m
2026-06-16 NDU28 - Jun 16, 12:05 UTCJun 16, 13:30 UTC1h 25m
2026-06-16 NDU28 - Jun 16, 02:45 UTCJun 16, 03:05 UTC20m
2026-06-12 NDU28 - Jun 12, 00:55 UTCJun 12, 02:05 UTC1h 10m
2026-06-11 NDU28 - Jun 11, 04:05 UTCJun 11, 05:45 UTC1h 40m
2026-06-09 NDU28 - Jun 9, 15:05 UTCJun 9, 15:20 UTC15m
2026-06-09 NDU28 - Jun 9, 00:45 UTCJun 9, 01:05 UTC20m
2026-06-08 NDU28 - Jun 8, 20:50 UTCJun 8, 21:25 UTC35m
2026-06-08 NDU28 - Jun 8, 15:45 UTCJun 8, 16:00 UTC15m
2026-06-06 NDU28 - Jun 6, 19:44 UTCJun 6, 21:00 UTC1h 15m
2026-05-30 NDU28 - May 30, 13:15 UTCMay 30, 13:50 UTC35m
2026-05-29 NDU28 - May 29, 20:30 UTCMay 29, 21:10 UTC40m
2026-05-29 NDU28 - May 29, 13:40 UTCMay 29, 14:15 UTC35m
2026-05-29 NDU28 - May 29, 03:50 UTCMay 29, 04:25 UTC35m
2026-05-29 NDU28 - May 29, 01:50 UTCMay 29, 03:05 UTC1h 15m
2026-05-28 NDU28 - May 28, 22:25 UTCMay 28, 22:50 UTC25m
2026-05-28 NDU28 - May 28, 20:15 UTCMay 28, 20:40 UTC25m
2026-05-28 NDU28 - May 28, 18:05 UTCMay 28, 18:30 UTC25m
2026-05-28 NDU28 - May 28, 16:00 UTCMay 28, 16:20 UTC20m
2026-05-28 NDU28 - May 28, 03:50 UTCMay 28, 04:00 UTC10m

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 N428ND page for operator, model, and routing details .

Mode-S A51A87 frequently asked

What is Mode-S code A51A87?
A51A87 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N428ND.
Where is Mode-S A51A87 registered?
Mode-S code A51A87 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 A51A87 broadcasting right now?
No active broadcast right now. Last signal was 20h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A51A87, octal 51215207, decimal 10,820,231.
What flights does A51A87 operate?
Mode-S A51A87 has broadcast 2 distinct callsigns, including NDU28, N428ND.