Apparatus

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sensors Mode-S transponder

A1977D

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N201UA · MOONEY M-20 · operated by ALLARD AVIATION LLC

Hex
A1977D
Octal
50313575
Decimal
10,590,077
Country
US
Tail
N201UA
Type
M20P
No current signal · last broadcast 7d ago
Flights observed
50
Distinct callsigns
3
Country
US
Last broadcast
7d ago

Last known position

Most recent position reported by Mode-S A1977D.

Country allocation

The ICAO 24-bit address A1977D 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 3 distinct

Callsign Airline Flights Last seen
N201UA - 38 2026-07-06
NGF1083 - 10 2026-07-06
SYH4642 - 2 2026-06-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-06 N201UA LEB → ASH Jul 6, 22:10 UTCJul 6, 22:50 UTC40m
2026-07-06 NGF1083 - Jul 6, 20:30 UTCJul 6, 21:55 UTC1h 25m
2026-07-02 N201UA - Jul 2, 22:15 UTCJul 2, 23:35 UTC1h 20m
2026-07-02 N201UA - Jul 2, 21:20 UTCJul 2, 21:40 UTC20m
2026-07-02 NGF1083 BOS → BGR Jul 2, 19:35 UTCJul 2, 21:05 UTC1h 30m
2026-07-02 N201UA - Jul 2, 18:15 UTCJul 2, 18:40 UTC25m
2026-06-26 N201UA - Jun 26, 22:10 UTCJun 26, 23:55 UTC1h 45m
2026-06-26 N201UA - Jun 26, 19:39 UTCJun 26, 21:39 UTC2h 0m
2026-06-26 NGF1083 - Jun 26, 17:44 UTCJun 26, 18:44 UTC1h 0m
2026-06-26 NGF1083 - Jun 26, 16:35 UTCJun 26, 17:09 UTC35m
2026-06-26 N201UA - Jun 26, 14:29 UTCJun 26, 15:54 UTC1h 25m
2026-06-25 N201UA - Jun 25, 16:45 UTCJun 25, 17:05 UTC20m
2026-06-25 N201UA - Jun 25, 15:50 UTCJun 25, 16:09 UTC20m
2026-06-24 N201UA - Jun 24, 20:14 UTCJun 24, 20:24 UTC10m
2026-06-24 NGF1083 - Jun 24, 17:05 UTCJun 24, 19:24 UTC2h 20m
2026-06-24 N201UA - Jun 24, 15:39 UTCJun 24, 16:34 UTC55m
2026-06-24 N201UA - Jun 24, 13:50 UTCJun 24, 14:34 UTC45m
2026-06-20 N201UA - Jun 20, 15:44 UTCJun 20, 16:55 UTC1h 10m
2026-06-16 N201UA - Jun 16, 20:05 UTCJun 17, 01:10 UTC5h 5m
2026-06-16 SYH4642 - Jun 16, 15:20 UTCJun 16, 19:25 UTC4h 5m
2026-06-16 N201UA ASH → CDW Jun 16, 13:00 UTCJun 16, 14:45 UTC1h 45m
2026-06-12 N201UA - Jun 12, 00:30 UTCJun 12, 00:45 UTC15m
2026-06-11 N201UA - Jun 11, 22:15 UTCJun 11, 23:55 UTC1h 40m
2026-06-11 NGF1083 BED → BGR Jun 11, 20:20 UTCJun 11, 22:00 UTC1h 40m
2026-06-11 N201UA ASH → BED Jun 11, 19:20 UTCJun 11, 19:35 UTC15m
2026-06-09 N201UA - Jun 9, 22:25 UTCJun 9, 22:45 UTC20m
2026-06-09 NGF1083 - Jun 9, 19:25 UTCJun 9, 21:45 UTC2h 20m
2026-06-09 N201UA - Jun 9, 17:10 UTCJun 9, 18:40 UTC1h 30m
2026-06-05 N201UA - Jun 5, 00:10 UTCJun 5, 00:30 UTC20m
2026-06-04 N201UA - Jun 4, 21:50 UTCJun 4, 23:30 UTC1h 40m
2026-06-04 NGF1083 BED → BGR Jun 4, 20:00 UTCJun 4, 21:30 UTC1h 30m
2026-06-04 N201UA - Jun 4, 17:55 UTCJun 4, 19:25 UTC1h 30m
2026-06-04 N201UA - Jun 4, 16:30 UTCJun 4, 16:50 UTC20m
2026-06-03 N201UA - Jun 3, 19:50 UTCJun 3, 20:10 UTC20m
2026-06-03 N201UA - Jun 3, 18:50 UTCJun 3, 19:15 UTC25m
2026-06-03 SYH4642 - Jun 3, 17:40 UTCJun 3, 18:15 UTC35m
2026-06-03 N201UA - Jun 3, 15:45 UTCJun 3, 16:20 UTC35m
2026-06-02 N201UA - Jun 2, 22:05 UTCJun 2, 22:25 UTC20m
2026-06-02 N201UA - Jun 2, 20:35 UTCJun 2, 21:15 UTC40m
2026-06-02 N201UA - Jun 2, 19:35 UTCJun 2, 19:55 UTC20m
2026-06-02 NGF1083 - Jun 2, 18:40 UTCJun 2, 19:00 UTC20m
2026-06-02 NGF1083 - Jun 2, 17:30 UTCJun 2, 18:00 UTC30m
2026-06-02 N201UA - Jun 2, 16:30 UTCJun 2, 16:40 UTC10m
2026-05-12 N201UA - May 12, 19:10 UTCMay 12, 19:30 UTC20m
2026-05-12 N201UA - May 12, 17:55 UTCMay 12, 18:30 UTC35m
2026-05-12 N201UA ASH → BVY May 12, 16:55 UTCMay 12, 17:10 UTC15m
2026-04-21 N201UA - Apr 21, 19:40 UTCApr 21, 20:00 UTC20m
2026-04-21 N201UA - Apr 21, 12:50 UTCApr 21, 13:05 UTC15m
2026-04-14 N201UA BVY → ASH Apr 14, 20:30 UTCApr 14, 20:50 UTC20m
2026-04-13 N201UA ASH → ASH Apr 13, 15:55 UTCApr 13, 16:05 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 N201UA page for operator, model, and routing details .

Mode-S A1977D frequently asked

What is Mode-S code A1977D?
A1977D is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N201UA.
Where is Mode-S A1977D registered?
Mode-S code A1977D 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 A1977D broadcasting right now?
No active broadcast right now. Last signal was 7d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1977D, octal 50313575, decimal 10,590,077.
What flights does A1977D operate?
Mode-S A1977D has broadcast 3 distinct callsigns, including N201UA, NGF1083, SYH4642.