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sensors Mode-S transponder

ADA21A

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N978HP · AEROSPATIALE AS-350 Ecureuil · operated by CALIFORNIA HIGHWAY PATROL, OFFICE OF AIR OPERATIONS

Hex
ADA21A
Octal
53321032
Decimal
11,379,226
Country
US
Tail
N978HP
Type
AS50
No current signal · last broadcast Jul 26, 21:35 UTC
Flights observed
99
Distinct callsigns
2
Country
US
Last broadcast
Jul 26, 21:35 UTC

Last known position

Most recent position reported by Mode-S ADA21A.

Country allocation

The ICAO 24-bit address ADA21A 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
N978HP - 98 2026-07-26
CHP24 - 1 2026-06-18

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 N978HP - Jul 26, 21:25 UTCJul 26, 21:35 UTC10m
2026-07-26 N978HP - Jul 26, 13:55 UTCJul 26, 14:15 UTC20m
2026-07-25 N978HP - Jul 25, 21:15 UTCJul 25, 21:30 UTC15m
2026-07-25 N978HP - Jul 25, 13:50 UTCJul 25, 14:05 UTC15m
2026-07-24 N978HP - Jul 24, 23:10 UTCJul 24, 23:25 UTC15m
2026-07-24 N978HP - Jul 24, 16:10 UTCJul 24, 16:20 UTC10m
2026-07-24 N978HP - Jul 24, 00:10 UTCJul 24, 00:25 UTC15m
2026-07-23 N978HP - Jul 23, 15:20 UTCJul 23, 15:30 UTC10m
2026-07-23 N978HP - Jul 23, 13:45 UTCJul 23, 14:15 UTC30m
2026-07-23 N978HP - Jul 23, 12:30 UTCJul 23, 12:55 UTC25m
2026-07-23 N978HP - Jul 23, 01:35 UTCJul 23, 01:45 UTC10m
2026-07-22 N978HP - Jul 22, 18:50 UTCJul 22, 19:25 UTC35m
2026-07-22 N978HP - Jul 22, 15:15 UTCJul 22, 15:25 UTC10m
2026-07-21 N978HP - Jul 21, 21:20 UTCJul 21, 21:30 UTC10m
2026-07-21 N978HP - Jul 21, 16:30 UTCJul 21, 16:45 UTC15m
2026-07-19 N978HP RDD → BZF Jul 19, 23:30 UTCJul 20, 00:00 UTC30m
2026-07-19 N978HP - Jul 19, 20:15 UTCJul 19, 21:45 UTC1h 30m
2026-07-19 N978HP - Jul 19, 18:25 UTCJul 19, 18:50 UTC25m
2026-07-19 N978HP - Jul 19, 01:55 UTCJul 19, 02:35 UTC40m
2026-07-18 N978HP - Jul 18, 22:40 UTCJul 18, 23:10 UTC30m
2026-07-18 N978HP - Jul 18, 20:35 UTCJul 18, 21:55 UTC1h 20m
2026-07-17 N978HP - Jul 17, 12:04 UTCJul 17, 12:30 UTC25m
2026-07-16 N978HP - Jul 16, 19:40 UTCJul 16, 19:50 UTC10m
2026-07-16 N978HP - Jul 16, 18:55 UTCJul 16, 19:10 UTC15m
2026-07-15 N978HP BZF → BZF Jul 15, 23:00 UTCJul 16, 00:25 UTC1h 25m
2026-07-15 N978HP - Jul 15, 15:45 UTCJul 15, 16:40 UTC55m
2026-07-15 N978HP - Jul 15, 15:10 UTCJul 15, 15:40 UTC30m
2026-07-15 N978HP - Jul 15, 12:00 UTCJul 15, 13:00 UTC1h 0m
2026-07-14 N978HP BZF → BZF Jul 14, 22:10 UTCJul 14, 22:20 UTC10m
2026-07-14 N978HP - Jul 14, 18:40 UTCJul 14, 19:35 UTC55m
2026-07-08 N978HP - Jul 8, 00:00 UTCJul 8, 00:35 UTC35m
2026-07-05 N978HP - Jul 5, 03:30 UTCJul 5, 04:25 UTC55m
2026-07-04 N978HP - Jul 4, 23:55 UTCJul 5, 01:25 UTC1h 30m
2026-07-04 N978HP BZF → RDD Jul 4, 23:40 UTCJul 4, 23:50 UTC10m
2026-07-04 N978HP - Jul 4, 21:05 UTCJul 4, 21:20 UTC15m
2026-07-04 N978HP - Jul 4, 03:55 UTCJul 4, 04:15 UTC20m
2026-07-04 N978HP - Jul 4, 02:25 UTCJul 4, 02:40 UTC15m
2026-07-04 N978HP - Jul 4, 01:20 UTCJul 4, 01:55 UTC35m
2026-07-04 N978HP - Jul 4, 00:30 UTCJul 4, 00:45 UTC15m
2026-07-03 N978HP - Jul 3, 21:35 UTCJul 3, 21:55 UTC20m
2026-07-02 N978HP - Jul 2, 22:40 UTCJul 2, 23:45 UTC1h 5m
2026-07-02 N978HP - Jul 2, 21:35 UTCJul 2, 21:45 UTC10m
2026-07-02 N978HP MCC → BZF Jul 2, 19:30 UTCJul 2, 20:40 UTC1h 10m
2026-07-02 N978HP - Jul 2, 18:25 UTCJul 2, 18:40 UTC15m
2026-07-02 N978HP - Jul 2, 17:40 UTCJul 2, 18:20 UTC40m
2026-07-02 N978HP - Jul 2, 15:55 UTCJul 2, 16:15 UTC20m
2026-07-02 N978HP - Jul 2, 14:10 UTCJul 2, 15:20 UTC1h 10m
2026-07-01 N978HP BZF → BZF Jul 1, 23:45 UTCJul 2, 00:10 UTC25m
2026-07-01 N978HP - Jul 1, 20:35 UTCJul 1, 21:25 UTC50m
2026-07-01 N978HP - Jul 1, 02:50 UTCJul 1, 03:05 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 N978HP page for operator, model, and routing details .

Mode-S ADA21A frequently asked

What is Mode-S code ADA21A?
ADA21A is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N978HP.
Where is Mode-S ADA21A registered?
Mode-S code ADA21A 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 ADA21A broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:35 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex ADA21A, octal 53321032, decimal 11,379,226.
What flights does ADA21A operate?
Mode-S ADA21A has broadcast 2 distinct callsigns, including N978HP, CHP24.