Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A4B420

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N402AS · BOEING 737-900 · operated by ALASKA AIRLINES INC

Hex
A4B420
Octal
51132040
Decimal
10,794,016
Country
US
Tail
N402AS
Type
B739
Broadcasting now · callsign ASA19 · 16,925 ft
Flights observed
461
Distinct callsigns
20
Country
US
Last broadcast
Jul 25, 06:55 UTC

Current position

A4B420 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A4B420 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 20 distinct

Callsign Airline Flights Last seen
ASA572 - 9 2026-07-14
ASA507 Alaska Airlines 7 2026-07-24
ASA349 Alaska Airlines 7 2026-05-09
ASA569 Alaska Airlines 6 2026-07-22
ASA623 - 4 2026-06-16
ASA618 - 4 2026-06-25
ASA563 - 4 2026-06-24
ASA500 - 4 2026-06-15
ASA494 - 4 2026-06-30
ASA365 - 4 2026-06-28
ASA304 Alaska Airlines 4 2026-06-19
ASA24 Alaska Airlines 4 2026-07-01
ASA1540 - 4 2026-07-09
ASA1385 Alaska Airlines 4 2026-06-04
ASA84 Alaska Airlines 3 2026-06-02
ASA735 Alaska Airlines 3 2026-06-02
ASA727 - 3 2026-06-22
ASA719 Alaska Airlines 3 2026-07-24
ASA684 Alaska Airlines 3 2026-05-07
ASA676 - 3 2026-06-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-25 ASA667 SEA → RDM Jul 25, 03:45 UTCJul 25, 06:50 UTC3h 5m
2026-07-24 ASA507 SNA → SEA Jul 24, 20:30 UTCJul 25, 00:15 UTC3h 45m
2026-07-24 ASA507 SNA → SEA Jul 24, 16:05 UTCJul 24, 19:15 UTC3h 10m
2026-07-24 ASA719 LAX → PDX Jul 24, 03:05 UTCJul 24, 04:45 UTC1h 40m
2026-07-24 ASA719 LAX → PDX Jul 24, 03:02 UTCJul 24, 04:34 UTC1h 32m
2026-07-24 ASA373 SJC → SJD Jul 24, 00:05 UTCJul 24, 01:40 UTC1h 35m
2026-07-23 ASA762 PDX → PHX Jul 23, 21:25 UTCJul 23, 22:30 UTC1h 5m
2026-07-23 ASA762 PDX → PHX Jul 23, 17:20 UTCJul 23, 17:35 UTC15m
2026-07-23 ASA761 SEA → SJC Jul 23, 07:20 UTCJul 23, 07:45 UTC25m
2026-07-23 ASA761 SEA → SJC Jul 23, 02:10 UTCJul 23, 02:40 UTC30m
2026-07-22 ASA567 PDX → SJD Jul 22, 22:15 UTCJul 23, 00:15 UTC2h 0m
2026-07-22 ASA565 LAX → PDX Jul 22, 18:35 UTCJul 22, 20:50 UTC2h 15m
2026-07-22 ASA281 EWR → SEA Jul 22, 12:25 UTCJul 22, 16:40 UTC4h 15m
2026-07-22 ASA569 MSY → SEA Jul 22, 00:30 UTCJul 22, 04:50 UTC4h 20m
2026-07-21 ASA568 SJC → SEA Jul 21, 18:55 UTCJul 21, 23:10 UTC4h 15m
2026-07-21 ASA1314 SJC → SEA Jul 21, 13:35 UTCJul 21, 15:10 UTC1h 35m
2026-07-21 ASA523 RNO → SEA Jul 21, 05:53 UTCJul 21, 07:30 UTC1h 37m
2026-07-21 ASA523 RNO → SEA Jul 21, 05:45 UTCJul 21, 07:30 UTC1h 45m
2026-07-21 ASA249 DEN → SEA Jul 21, 01:20 UTCJul 21, 03:45 UTC2h 25m
2026-07-20 ASA242 MKE → SEA Jul 20, 21:40 UTCJul 21, 00:00 UTC2h 19m
2026-07-20 ASA720 SEA → OAK Jul 20, 17:30 UTCJul 20, 19:30 UTC2h 0m
2026-07-20 ASA488 SEA → IND Jul 20, 13:55 UTCJul 20, 16:05 UTC2h 10m
2026-07-19 ASA517 FLL → SEA Jul 19, 23:10 UTCJul 20, 04:50 UTC5h 40m
2026-07-19 ASA516 SEA → FLL Jul 19, 15:50 UTCJul 19, 21:20 UTC5h 30m
2026-07-19 ASA206 PDX → SFO Jul 19, 12:40 UTCJul 19, 13:30 UTC50m
2026-07-19 ASA353 - Jul 19, 06:45 UTCJul 19, 06:55 UTC10m
2026-07-19 ASA353 - Jul 19, 01:35 UTCJul 19, 02:25 UTC50m
2026-07-18 ASA742 PHX → PDX Jul 18, 22:05 UTCJul 19, 00:15 UTC2h 10m
2026-07-18 ASA593 SEA → PHX Jul 18, 18:00 UTCJul 18, 20:45 UTC2h 45m
2026-07-18 ASA444 SEA → PHL Jul 18, 14:30 UTCJul 18, 16:30 UTC2h 0m
2026-07-18 ASA1408 SJC → GDL Jul 18, 03:05 UTCJul 18, 05:20 UTC2h 15m
2026-07-18 ASA296 - Jul 18, 00:25 UTCJul 18, 01:25 UTC1h 0m
2026-07-18 ASA296 BOI → SEA Jul 18, 00:22 UTCJul 18, 01:15 UTC53m
2026-07-17 ASA342 - Jul 17, 22:05 UTCJul 17, 23:00 UTC55m
2026-07-17 ASA251 GEG → PDX Jul 17, 19:55 UTCJul 17, 20:44 UTC50m
2026-07-17 ASA250 PDX → GEG Jul 17, 17:35 UTCJul 17, 18:19 UTC45m
2026-07-17 ASA541 AUS → PDX Jul 17, 12:35 UTCJul 17, 16:15 UTC3h 40m
2026-07-17 ASA372 SEA → AUS Jul 17, 02:39 UTCJul 17, 06:20 UTC3h 40m
2026-07-16 ASA439 - Jul 16, 19:55 UTCJul 16, 23:55 UTC4h 0m
2026-07-16 ASA1420 - Jul 16, 14:40 UTCJul 16, 18:29 UTC3h 50m
2026-07-15 ASA301 MCO → PDX Jul 15, 21:45 UTCJul 16, 02:55 UTC5h 10m
2026-07-15 ASA295 SEA → MCO Jul 15, 15:15 UTCJul 15, 20:30 UTC5h 15m
2026-07-14 ASA572 - Jul 14, 22:25 UTCJul 15, 03:10 UTC4h 44m
2026-07-14 ASA572 SEA → RDU Jul 14, 16:10 UTCJul 14, 21:05 UTC4h 55m
2026-07-14 ASA1375 - Jul 14, 00:25 UTCJul 14, 02:30 UTC2h 5m
2026-07-13 ASA502 - Jul 13, 20:30 UTCJul 13, 22:55 UTC2h 25m
2026-07-13 ASA338 BOS → SEA Jul 13, 13:30 UTCJul 13, 19:00 UTC5h 30m
2026-07-13 ASA536 SEA → BOS Jul 13, 06:45 UTCJul 13, 11:40 UTC4h 55m
2026-07-12 ASA569 MSY → SEA Jul 12, 22:55 UTCJul 13, 03:20 UTC4h 25m
2026-07-12 ASA568 SEA → MSY Jul 12, 17:20 UTCJul 12, 21:40 UTC4h 20m

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 N402AS page for operator, model, and routing details .

Mode-S A4B420 frequently asked

What is Mode-S code A4B420?
A4B420 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N402AS.
Where is Mode-S A4B420 registered?
Mode-S code A4B420 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 A4B420 broadcasting right now?
Yes. Mode-S A4B420 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A4B420, octal 51132040, decimal 10,794,016.
What flights does A4B420 operate?
Mode-S A4B420 has broadcast 20 distinct callsigns, including ASA572, ASA507, ASA349, ASA569, ASA623.