Apparatus

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sensors Mode-S transponder

AA4440

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N76021 · BOEING 777-200 · operated by UNITED AIRLINES INC

Hex
AA4440
Octal
52442100
Decimal
11,158,592
Country
US
Tail
N76021
Type
B772
Broadcasting now · callsign UAL984 · 18,275 ft
Flights observed
219
Distinct callsigns
20
Country
US
Last broadcast
2h ago

Current position

AA4440 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address AA4440 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
UAL672 - 11 2026-07-03
UAL57 - 9 2026-07-13
UAL852 - 8 2026-06-30
UAL969 - 7 2026-06-13
UAL853 - 7 2026-06-29
UAL58 - 7 2026-07-01
UAL984 - 6 2026-07-09
UAL949 United Airlines 6 2026-06-03
UAL889 United Airlines 6 2026-06-12
UAL888 United Airlines 6 2026-06-11
UAL673 - 6 2026-07-03
UAL59 - 6 2026-07-02
UAL507 - 6 2026-06-28
UAL968 - 5 2026-06-12
UAL948 United Airlines 5 2026-04-15
UAL875 - 5 2026-06-19
UAL44 United Airlines 5 2026-06-14
UAL23 - 5 2026-07-06
UAL914 - 4 2026-07-12
UAL884 United Airlines 4 2026-05-26

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 UAL57 EWR → CDG Jul 13, 22:15 UTCJul 14, 05:00 UTC6h 45m
2026-07-13 UAL56 - Jul 13, 08:35 UTCJul 13, 10:10 UTC1h 35m
2026-07-13 UAL56 CDG → EWR Jul 13, 08:49 UTCJul 13, 15:44 UTC6h 55m
2026-07-12 UAL915 IAD → CDG Jul 12, 23:11 UTCJul 13, 06:17 UTC7h 6m
2026-07-12 UAL915 - Jul 12, 23:20 UTCJul 13, 06:01 UTC6h 40m
2026-07-12 UAL914 - Jul 12, 10:55 UTCJul 12, 18:30 UTC7h 35m
2026-07-11 UAL990 SFO → CDG Jul 11, 22:10 UTCJul 12, 08:10 UTC10h 0m
2026-07-11 UAL34 - Jul 11, 08:25 UTCJul 11, 18:10 UTC9h 45m
2026-07-10 UAL35 SFO → KIX Jul 10, 18:35 UTCJul 11, 05:59 UTC11h 24m
2026-07-10 UAL35 SFO → KIX Jul 10, 18:50 UTCJul 11, 06:35 UTC11h 45m
2026-07-09 UAL984 - Jul 9, 07:45 UTCJul 9, 10:00 UTC2h 15m
2026-07-09 UAL984 CDG → SFO Jul 9, 07:54 UTCJul 9, 18:14 UTC10h 20m
2026-07-09 UAL984 CDG → SFO Jul 9, 07:54 UTCJul 9, 18:10 UTC10h 16m
2026-07-08 UAL57 EWR → CDG Jul 8, 23:13 UTCJul 9, 05:41 UTC6h 28m
2026-07-08 UAL57 EWR → CDG Jul 8, 23:05 UTCJul 9, 00:50 UTC1h 45m
2026-07-08 UAL71 - Jul 8, 07:35 UTCJul 8, 14:50 UTC7h 15m
2026-07-07 UAL70 EWR → AMS Jul 7, 22:33 UTCJul 8, 05:01 UTC6h 28m
2026-07-07 UAL70 EWR → AMS Jul 7, 22:40 UTCJul 8, 05:10 UTC6h 30m
2026-07-07 UAL121 BCN → EWR Jul 7, 11:41 UTCJul 7, 19:49 UTC8h 8m
2026-07-07 UAL121 - Jul 7, 12:20 UTCJul 7, 13:50 UTC1h 30m
2026-07-06 UAL120 EWR → BCN Jul 6, 23:40 UTCJul 7, 06:45 UTC7h 5m
2026-07-06 UAL22 DUB → EWR Jul 6, 08:40 UTCJul 6, 15:25 UTC6h 45m
2026-07-06 UAL23 EWR → DUB Jul 6, 00:32 UTCJul 6, 06:02 UTC5h 30m
2026-07-06 UAL23 - Jul 6, 00:50 UTCJul 6, 02:00 UTC1h 10m
2026-07-05 UAL121 - Jul 5, 13:50 UTCJul 5, 21:30 UTC7h 40m
2026-07-05 UAL120 EWR → BCN Jul 5, 04:30 UTCJul 5, 11:10 UTC6h 40m
2026-07-04 UAL2416 SFO → EWR Jul 4, 08:11 UTCJul 4, 13:00 UTC4h 49m
2026-07-04 UAL2416 SFO → EWR Jul 4, 08:05 UTCJul 4, 12:55 UTC4h 50m
2026-07-03 UAL673 BCN → SFO Jul 3, 15:25 UTCJul 4, 02:55 UTC11h 30m
2026-07-03 UAL672 SFO → BCN Jul 3, 01:29 UTCJul 3, 11:43 UTC10h 14m
2026-07-03 UAL672 SFO → BCN Jul 3, 01:25 UTCJul 3, 11:55 UTC10h 30m
2026-07-02 UAL59 - Jul 2, 11:20 UTCJul 2, 22:00 UTC10h 40m
2026-07-01 UAL58 SFO → FRA Jul 1, 21:35 UTCJul 2, 07:40 UTC10h 5m
2026-06-30 UAL852 - Jun 30, 09:00 UTCJun 30, 17:45 UTC8h 45m
2026-06-30 UAL852 - Jun 30, 06:50 UTCJun 30, 07:05 UTC15m
2026-06-30 UAL852 TPE → SFO Jun 30, 06:51 UTCJun 30, 17:57 UTC11h 6m
2026-06-29 UAL853 SFO → TPE Jun 29, 07:46 UTCJun 29, 20:18 UTC12h 32m
2026-06-29 UAL853 - Jun 29, 07:50 UTCJun 29, 20:19 UTC12h 30m
2026-06-28 UAL506 - Jun 28, 14:25 UTCJun 28, 17:10 UTC2h 45m
2026-06-28 UAL506 FCO → SFO Jun 28, 14:07 UTCJun 29, 02:03 UTC11h 56m
2026-06-28 UAL507 SFO → FCO Jun 28, 00:19 UTCJun 28, 11:35 UTC11h 16m
2026-06-28 UAL507 - Jun 28, 00:20 UTCJun 28, 11:39 UTC11h 20m
2026-06-27 UAL195 MUC → SFO Jun 27, 10:05 UTCJun 27, 20:59 UTC10h 55m
2026-06-27 UAL195 MUC → SFO Jun 27, 10:02 UTCJun 27, 20:55 UTC10h 53m
2026-06-26 UAL102 - Jun 26, 22:10 UTCJun 27, 07:34 UTC9h 25m
2026-06-26 UAL102 IAH → MUC Jun 26, 22:02 UTCJun 27, 07:30 UTC9h 28m
2026-06-26 UAL879 - Jun 26, 09:14 UTCJun 26, 19:00 UTC9h 45m
2026-06-25 UAL14 EWR → LHR Jun 25, 23:35 UTCJun 26, 05:45 UTC6h 10m
2026-06-25 UAL14 - Jun 25, 23:39 UTCJun 26, 05:50 UTC6h 10m
2026-06-25 UAL3940 - Jun 25, 00:35 UTCJun 25, 09:40 UTC9h 5m

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 N76021 page for operator, model, and routing details .

Mode-S AA4440 frequently asked

What is Mode-S code AA4440?
AA4440 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N76021.
Where is Mode-S AA4440 registered?
Mode-S code AA4440 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 AA4440 broadcasting right now?
Yes. Mode-S AA4440 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AA4440, octal 52442100, decimal 11,158,592.
What flights does AA4440 operate?
Mode-S AA4440 has broadcast 20 distinct callsigns, including UAL672, UAL57, UAL852, UAL969, UAL853.