Apparatus

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sensors Mode-S transponder

A4423A

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N37367 · BOEING 737 MAX 8 · operated by UNITED AIRLINES INC

Hex
A4423A
Octal
51041072
Decimal
10,764,858
Country
US
Tail
N37367
Type
B38M
No current signal · last broadcast 3h ago
Flights observed
413
Distinct callsigns
20
Country
US
Last broadcast
3h ago

Last known position

Most recent position reported by Mode-S A4423A.

Country allocation

The ICAO 24-bit address A4423A 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
UAL2007 - 6 2026-07-04
UAL474 - 5 2026-07-10
UAL359 - 5 2026-07-10
UAL2224 United Airlines 5 2026-06-13
UAL1352 - 5 2026-07-08
UAL2386 - 4 2026-06-24
UAL2123 United Airlines 4 2026-04-17
UAL1751 - 4 2026-07-04
UAL1523 United Airlines 4 2026-06-03
UAL1415 - 4 2026-07-02
UAL1320 - 4 2026-07-08
UAL1194 United Airlines 4 2026-04-15
UAL784 - 3 2026-04-13
UAL757 - 3 2026-07-13
UAL660 - 3 2026-07-10
UAL587 United Airlines 3 2026-04-30
UAL394 United Airlines 3 2026-05-23
UAL275 United Airlines 3 2026-05-19
UAL2426 United Airlines 3 2026-04-26
UAL2234 United Airlines 3 2026-04-19

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 UAL8168 DEN → LGA Jul 13, 22:21 UTCJul 14, 01:39 UTC3h 18m
2026-07-13 UAL8168 DEN → LGA Jul 13, 22:10 UTCJul 14, 01:40 UTC3h 30m
2026-07-13 UAL757 BFI → DEN Jul 13, 18:15 UTCJul 13, 20:25 UTC2h 10m
2026-07-13 UAL2271 DEN → SEA Jul 13, 14:20 UTCJul 13, 16:30 UTC2h 10m
2026-07-13 UAL361 AUS → DEN Jul 13, 10:50 UTCJul 13, 12:40 UTC1h 50m
2026-07-13 UAL1942 DEN → AUS Jul 13, 01:10 UTCJul 13, 02:55 UTC1h 45m
2026-07-12 UAL517 - Jul 12, 19:40 UTCJul 12, 23:05 UTC3h 25m
2026-07-12 UAL517 BTV → DEN Jul 12, 19:47 UTCJul 12, 22:58 UTC3h 11m
2026-07-12 UAL786 ORD → BTV Jul 12, 16:20 UTCJul 12, 18:01 UTC1h 40m
2026-07-12 UAL2653 - Jul 12, 12:30 UTCJul 12, 13:55 UTC1h 25m
2026-07-12 UAL8100 - Jul 12, 03:05 UTCJul 12, 04:30 UTC1h 25m
2026-07-11 UAL1009 - Jul 11, 20:00 UTCJul 11, 23:45 UTC3h 45m
2026-07-11 UAL8188 - Jul 11, 14:45 UTCJul 11, 18:30 UTC3h 45m
2026-07-10 UAL474 - Jul 10, 20:40 UTCJul 11, 00:05 UTC3h 25m
2026-07-10 UAL474 MEX → ORD Jul 10, 20:28 UTCJul 10, 23:48 UTC3h 20m
2026-07-10 UAL359 - Jul 10, 18:25 UTCJul 10, 18:30 UTC5m
2026-07-10 UAL359 - Jul 10, 14:45 UTCJul 10, 17:50 UTC3h 5m
2026-07-10 UAL660 PHL → ORD Jul 10, 10:35 UTCJul 10, 12:35 UTC2h 0m
2026-07-10 UAL1744 ORD → PHL Jul 10, 04:25 UTCJul 10, 05:55 UTC1h 30m
2026-07-10 UAL1744 ORD → PHL Jul 10, 03:53 UTCJul 10, 05:52 UTC1h 59m
2026-07-09 UAL474 - Jul 9, 20:45 UTCJul 10, 00:20 UTC3h 35m
2026-07-09 UAL474 MEX → ORD Jul 9, 20:28 UTCJul 10, 00:04 UTC3h 36m
2026-07-09 UAL359 ORD → MEX Jul 9, 15:27 UTCJul 9, 18:49 UTC3h 22m
2026-07-09 UAL359 ORD → MEX Jul 9, 15:10 UTCJul 9, 18:55 UTC3h 45m
2026-07-09 UAL660 - Jul 9, 10:10 UTCJul 9, 11:50 UTC1h 40m
2026-07-09 UAL8144 ORD → PHL Jul 9, 03:40 UTCJul 9, 05:10 UTC1h 30m
2026-07-08 UAL1352 - Jul 8, 21:15 UTCJul 9, 01:10 UTC3h 55m
2026-07-08 UAL1320 - Jul 8, 17:45 UTCJul 8, 19:45 UTC2h 0m
2026-07-08 UAL2167 TPA → DEN Jul 8, 12:15 UTCJul 8, 15:25 UTC3h 10m
2026-07-07 UAL2375 DEN → TPA Jul 7, 20:20 UTCJul 7, 23:25 UTC3h 5m
2026-07-07 UAL2246 - Jul 7, 15:40 UTCJul 7, 18:15 UTC2h 35m
2026-07-07 UAL1833 EWR → CLE Jul 7, 13:15 UTCJul 7, 14:20 UTC1h 5m
2026-07-06 UAL1446 DEN → EWR Jul 6, 16:25 UTCJul 7, 03:15 UTC10h 50m
2026-07-06 UAL1607 IND → DEN Jul 6, 12:15 UTCJul 6, 14:25 UTC2h 10m
2026-07-06 UAL1607 IND → DEN Jul 6, 12:14 UTCJul 6, 14:22 UTC2h 8m
2026-07-06 UAL2477 - Jul 6, 06:55 UTCJul 6, 10:40 UTC3h 45m
2026-07-05 UAL2620 - Jul 5, 23:55 UTCJul 6, 05:05 UTC5h 10m
2026-07-05 UAL609 ORD → MCO Jul 5, 19:33 UTCJul 5, 21:50 UTC2h 17m
2026-07-05 UAL609 - Jul 5, 19:35 UTCJul 5, 22:00 UTC2h 25m
2026-07-05 UAL1057 LGA → ORD Jul 5, 15:40 UTCJul 5, 17:55 UTC2h 15m
2026-07-05 UAL3883 EWR → LGA Jul 5, 14:10 UTCJul 5, 14:35 UTC25m
2026-07-05 UAL2809 ORD → EWR Jul 5, 04:53 UTCJul 5, 06:02 UTC1h 9m
2026-07-05 UAL2809 ORD → EWR Jul 5, 04:40 UTCJul 5, 06:10 UTC1h 30m
2026-07-04 UAL2007 - Jul 4, 19:35 UTCJul 4, 23:15 UTC3h 40m
2026-07-04 UAL2007 - Jul 4, 18:50 UTCJul 4, 19:00 UTC10m
2026-07-04 UAL2007 GUA → ORD Jul 4, 18:47 UTCJul 4, 23:14 UTC4h 27m
2026-07-04 UAL1751 - Jul 4, 17:00 UTCJul 4, 17:15 UTC15m
2026-07-04 UAL1751 - Jul 4, 14:55 UTCJul 4, 15:15 UTC20m
2026-07-04 UAL2393 JAX → EWR Jul 4, 12:25 UTCJul 4, 13:00 UTC35m
2026-07-04 UAL1942 DEN → AUS Jul 4, 03:30 UTCJul 4, 05:10 UTC1h 40m

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 N37367 page for operator, model, and routing details .

Mode-S A4423A frequently asked

What is Mode-S code A4423A?
A4423A is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N37367.
Where is Mode-S A4423A registered?
Mode-S code A4423A 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 A4423A broadcasting right now?
No active broadcast right now. Last signal was 3h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A4423A, octal 51041072, decimal 10,764,858.
What flights does A4423A operate?
Mode-S A4423A has broadcast 20 distinct callsigns, including UAL2007, UAL474, UAL359, UAL2224, UAL1352.