Apparatus

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sensors Mode-S transponder

A6B021

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N53X

Hex
A6B021
Octal
51530041
Decimal
10,924,065
Country
US
Tail
N53X
No current signal · last broadcast Jun 22, 17:34 UTC
Flights observed
41
Distinct callsigns
1
Country
US
Last broadcast
Jun 22, 17:34 UTC

Last known position

Most recent position reported by Mode-S A6B021.

Country allocation

The ICAO 24-bit address A6B021 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
N53X - 41 2026-06-22

Recent flights last 41

DateFlightRouteTakeoffLandingDuration
2026-06-22 N53X - Jun 22, 16:45 UTCJun 22, 17:29 UTC45m
2026-06-20 N53X - Jun 20, 18:29 UTCJun 20, 19:09 UTC40m
2026-06-17 N53X - Jun 17, 19:35 UTCJun 17, 19:50 UTC15m
2026-06-17 N53X - Jun 17, 05:25 UTCJun 17, 06:25 UTC1h 0m
2026-06-16 N53X - Jun 16, 20:50 UTCJun 16, 21:00 UTC10m
2026-06-16 N53X - Jun 16, 19:05 UTCJun 16, 19:15 UTC10m
2026-06-16 N53X - Jun 16, 02:04 UTCJun 16, 02:45 UTC40m
2026-06-15 N53X - Jun 15, 21:14 UTCJun 15, 21:50 UTC35m
2026-06-15 N53X - Jun 15, 19:10 UTCJun 15, 20:10 UTC1h 0m
2026-06-10 N53X - Jun 10, 15:55 UTCJun 10, 16:20 UTC25m
2026-06-09 N53X HOM → MRI Jun 9, 23:00 UTCJun 10, 00:00 UTC1h 0m
2026-06-09 N53X - Jun 9, 20:55 UTCJun 9, 21:50 UTC55m
2026-06-07 N53X - Jun 7, 20:30 UTCJun 7, 21:35 UTC1h 5m
2026-06-07 N53X - Jun 7, 20:10 UTCJun 7, 20:20 UTC10m
2026-06-07 N53X - Jun 7, 00:55 UTCJun 7, 01:35 UTC40m
2026-06-06 N53X - Jun 6, 23:39 UTCJun 7, 00:19 UTC40m
2026-06-06 N53X - Jun 6, 19:54 UTCJun 6, 20:39 UTC45m
2026-06-06 N53X - Jun 6, 19:30 UTCJun 6, 19:34 UTC5m
2026-06-06 N53X - Jun 6, 04:30 UTCJun 6, 04:35 UTC5m
2026-06-05 N53X - Jun 5, 22:00 UTCJun 5, 22:30 UTC30m
2026-06-05 N53X - Jun 5, 19:15 UTCJun 5, 19:45 UTC30m
2026-06-05 N53X - Jun 5, 18:30 UTCJun 5, 18:35 UTC5m
2026-06-05 N53X - Jun 5, 01:40 UTCJun 5, 02:15 UTC35m
2026-06-03 N53X TKA → TKA Jun 3, 18:45 UTCJun 3, 18:50 UTC5m
2026-06-03 N53X - Jun 3, 05:40 UTCJun 3, 06:25 UTC45m
2026-05-28 N53X HOM → MRI May 28, 01:40 UTCMay 28, 02:45 UTC1h 5m
2026-05-25 N53X - May 25, 21:24 UTCMay 25, 22:05 UTC40m
2026-05-25 N53X - May 25, 20:04 UTCMay 25, 20:50 UTC45m
2026-05-24 N53X - May 24, 21:25 UTCMay 24, 21:45 UTC20m
2026-05-24 N53X - May 24, 05:05 UTCMay 24, 05:35 UTC30m
2026-05-24 N53X - May 24, 04:05 UTCMay 24, 04:20 UTC15m
2026-05-22 N53X - May 22, 00:40 UTCMay 22, 01:05 UTC25m
2026-05-20 N53X - May 20, 19:05 UTCMay 20, 19:15 UTC10m
2026-05-19 N53X - May 19, 22:00 UTCMay 20, 00:20 UTC2h 20m
2026-05-19 N53X - May 19, 15:00 UTCMay 19, 15:20 UTC20m
2026-05-19 N53X - May 19, 03:05 UTCMay 19, 03:25 UTC20m
2026-05-15 N53X - May 15, 19:15 UTCMay 15, 20:15 UTC1h 0m
2026-05-15 N53X - May 15, 01:05 UTCMay 15, 01:40 UTC35m
2026-05-14 N53X - May 14, 21:30 UTCMay 14, 23:00 UTC1h 30m
2026-05-14 N53X - May 14, 17:30 UTCMay 14, 18:05 UTC35m
2026-05-14 N53X - May 14, 14:25 UTCMay 14, 15:01 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 N53X page for operator, model, and routing details .

Mode-S A6B021 frequently asked

What is Mode-S code A6B021?
A6B021 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N53X.
Where is Mode-S A6B021 registered?
Mode-S code A6B021 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 A6B021 broadcasting right now?
No active broadcast right now. Last signal was Jun 22, 17:34 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A6B021, octal 51530041, decimal 10,924,065.
What flights does A6B021 operate?
Mode-S A6B021 has broadcast 1 distinct callsign, including N53X.