Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A21F04

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N236CH · BEECH 36 Bonanza · operated by GTA AIR INC

Hex
A21F04
Octal
50417404
Decimal
10,624,772
Country
US
Tail
N236CH
Type
BE36
No current signal · last broadcast 2d ago
Flights observed
112
Distinct callsigns
17
Country
US
Last broadcast
2d ago

Last known position

Most recent position reported by Mode-S A21F04.

Country allocation

The ICAO 24-bit address A21F04 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 17 distinct

Callsign Airline Flights Last seen
GTX503 - 16 2026-07-14
GTX508 - 13 2026-05-09
GTX504 - 13 2026-07-08
GTX502 - 10 2026-06-09
GTX507 - 8 2026-06-25
GTX501 - 8 2026-07-13
GTX322 - 7 2026-07-11
GTX321 - 7 2026-07-15
GTX510 - 6 2026-04-24
GTX701 - 5 2026-06-25
GTX505 - 5 2026-07-09
GTX800 - 4 2026-06-15
GTX509 - 3 2026-06-20
GTX947 - 2 2026-07-02
GTX323 - 2 2026-07-09
GTX922 - 1 2026-05-21
GTX506 - 1 2026-06-12

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-15 GTX321 IAD → CMH Jul 15, 02:10 UTCJul 15, 03:50 UTC1h 40m
2026-07-14 GTX503 - Jul 14, 23:20 UTCJul 15, 01:00 UTC1h 40m
2026-07-14 GTX503 - Jul 14, 18:00 UTCJul 14, 21:25 UTC3h 25m
2026-07-13 GTX501 - Jul 13, 23:15 UTCJul 14, 02:55 UTC3h 40m
2026-07-13 GTX501 - Jul 13, 19:10 UTCJul 13, 21:15 UTC2h 5m
2026-07-11 GTX322 CMH → IAD Jul 11, 05:35 UTCJul 11, 10:10 UTC4h 35m
2026-07-11 GTX321 - Jul 11, 01:10 UTCJul 11, 02:55 UTC1h 45m
2026-07-10 GTX322 - Jul 10, 05:05 UTCJul 10, 10:00 UTC4h 55m
2026-07-10 GTX321 - Jul 10, 01:05 UTCJul 10, 02:50 UTC1h 45m
2026-07-09 GTX505 - Jul 9, 17:25 UTCJul 9, 18:30 UTC1h 5m
2026-07-09 GTX505 - Jul 9, 14:35 UTCJul 9, 16:30 UTC1h 55m
2026-07-09 GTX505 IAD → MMU Jul 9, 11:35 UTCJul 9, 12:50 UTC1h 15m
2026-07-09 GTX323 - Jul 9, 08:10 UTCJul 9, 09:45 UTC1h 35m
2026-07-09 GTX322 - Jul 9, 05:05 UTCJul 9, 07:40 UTC2h 35m
2026-07-09 GTX321 - Jul 9, 01:10 UTCJul 9, 03:00 UTC1h 50m
2026-07-08 GTX504 ROC → IAD Jul 8, 16:50 UTCJul 8, 18:35 UTC1h 45m
2026-07-08 GTX504 - Jul 8, 15:35 UTCJul 8, 15:50 UTC15m
2026-07-08 GTX504 - Jul 8, 14:35 UTCJul 8, 15:00 UTC25m
2026-07-08 GTX504 - Jul 8, 11:30 UTCJul 8, 12:45 UTC1h 15m
2026-07-08 GTX323 - Jul 8, 08:30 UTCJul 8, 10:10 UTC1h 40m
2026-07-08 GTX322 CMH → FRG Jul 8, 05:00 UTCJul 8, 07:50 UTC2h 50m
2026-07-08 GTX321 - Jul 8, 01:15 UTCJul 8, 02:55 UTC1h 40m
2026-07-06 GTX503 - Jul 6, 19:15 UTCJul 6, 20:15 UTC1h 0m
2026-07-06 GTX503 - Jul 6, 16:10 UTCJul 6, 18:10 UTC2h 0m
2026-07-06 GTX503 IAD → TEB Jul 6, 11:20 UTCJul 6, 12:50 UTC1h 30m
2026-07-03 GTX322 - Jul 3, 05:15 UTCJul 3, 09:55 UTC4h 40m
2026-07-03 GTX321 - Jul 3, 01:20 UTCJul 3, 03:10 UTC1h 50m
2026-07-02 GTX947 - Jul 2, 19:20 UTCJul 3, 00:10 UTC4h 50m
2026-07-01 GTX947 - Jul 1, 23:45 UTCJul 2, 00:50 UTC1h 5m
2026-06-25 GTX701 - Jun 25, 15:29 UTCJun 25, 17:30 UTC2h 0m
2026-06-25 GTX507 - Jun 25, 00:59 UTCJun 25, 02:39 UTC1h 40m
2026-06-24 GTX507 - Jun 24, 23:34 UTCJun 24, 23:54 UTC20m
2026-06-23 GTX507 - Jun 23, 07:19 UTCJun 23, 07:45 UTC25m
2026-06-23 GTX507 - Jun 23, 02:49 UTCJun 23, 05:24 UTC2h 35m
2026-06-22 GTX507 - Jun 22, 22:05 UTCJun 23, 00:39 UTC2h 35m
2026-06-22 GTX701 - Jun 22, 19:29 UTCJun 22, 21:14 UTC1h 45m
2026-06-22 GTX503 - Jun 22, 03:54 UTCJun 22, 04:59 UTC1h 5m
2026-06-22 GTX503 - Jun 22, 02:10 UTCJun 22, 03:05 UTC55m
2026-06-21 GTX503 - Jun 21, 23:50 UTCJun 22, 01:29 UTC1h 40m
2026-06-21 GTX503 - Jun 21, 07:59 UTCJun 21, 09:35 UTC1h 35m
2026-06-21 GTX503 - Jun 21, 02:50 UTCJun 21, 03:10 UTC20m
2026-06-20 GTX509 - Jun 20, 01:24 UTCJun 20, 04:20 UTC2h 55m
2026-06-15 GTX800 - Jun 15, 23:54 UTCJun 16, 03:10 UTC3h 15m
2026-06-13 GTX322 CMH → FRG Jun 13, 05:20 UTCJun 13, 07:55 UTC2h 35m
2026-06-13 GTX321 - Jun 13, 01:35 UTCJun 13, 03:20 UTC1h 45m
2026-06-12 GTX506 CMH → DPA Jun 12, 10:55 UTCJun 12, 13:05 UTC2h 10m
2026-06-09 GTX502 - Jun 9, 16:50 UTCJun 9, 17:50 UTC1h 0m
2026-06-09 GTX502 - Jun 9, 13:30 UTCJun 9, 14:30 UTC1h 0m
2026-06-09 GTX502 - Jun 9, 11:45 UTCJun 9, 12:25 UTC40m
2026-06-09 GTX503 - Jun 9, 02:10 UTCJun 9, 02:55 UTC45m

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 N236CH page for operator, model, and routing details .

Mode-S A21F04 frequently asked

What is Mode-S code A21F04?
A21F04 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N236CH.
Where is Mode-S A21F04 registered?
Mode-S code A21F04 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 A21F04 broadcasting right now?
No active broadcast right now. Last signal was 2d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A21F04, octal 50417404, decimal 10,624,772.
What flights does A21F04 operate?
Mode-S A21F04 has broadcast 17 distinct callsigns, including GTX503, GTX508, GTX504, GTX502, GTX507.