Apparatus

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sensors Mode-S transponder

A43E5E

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N37255 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
A43E5E
Octal
51037136
Decimal
10,763,870
Country
US
Tail
N37255
Type
B738
No current signal · last broadcast Jul 26, 20:55 UTC
Flights observed
146
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:55 UTC

Last known position

Most recent position reported by Mode-S A43E5E.

Country allocation

The ICAO 24-bit address A43E5E 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
UAL520 United Airlines 3 2026-07-24
UAL453 - 3 2026-07-09
UAL2160 United Airlines 3 2026-07-19
UAL1909 - 3 2026-07-09
UAL1693 - 3 2026-07-07
UAL8104 - 2 2026-07-13
UAL797 - 2 2026-06-27
UAL687 - 2 2026-07-10
UAL678 - 2 2026-06-26
UAL640 - 2 2026-07-13
UAL514 - 2 2026-07-15
UAL476 - 2 2026-07-15
UAL452 - 2 2026-07-11
UAL441 United Airlines 2 2026-07-19
UAL3910 - 2 2026-07-04
UAL334 - 2 2026-07-17
UAL329 - 2 2026-07-02
UAL294 - 2 2026-07-01
UAL2822 - 2 2026-07-06
UAL2648 - 2 2026-07-15

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL499 DEN → EWR Jul 26, 16:55 UTCJul 26, 20:50 UTC3h 55m
2026-07-26 UAL2153 DEN → SNA Jul 26, 10:40 UTCJul 26, 15:15 UTC4h 35m
2026-07-26 UAL2641 SFO → SAN Jul 26, 04:50 UTCJul 26, 08:55 UTC4h 6m
2026-07-26 UAL2641 SFO → SAN Jul 26, 04:47 UTCJul 26, 08:53 UTC4h 6m
2026-07-25 UAL1349 RSW → IAD Jul 25, 22:10 UTCJul 26, 02:45 UTC4h 35m
2026-07-25 UAL2039 LAX → ORD Jul 25, 16:20 UTCJul 25, 20:35 UTC4h 15m
2026-07-25 UAL2127 LGA → ORD Jul 25, 13:05 UTCJul 25, 14:00 UTC55m
2026-07-25 UAL2854 EWR → BZN Jul 25, 05:35 UTCJul 25, 06:35 UTC1h 0m
2026-07-25 UAL1321 MIA → EWR Jul 25, 01:15 UTCJul 25, 02:10 UTC55m
2026-07-25 UAL1321 MIA → EWR Jul 25, 01:30 UTCJul 25, 02:07 UTC37m
2026-07-24 UAL2823 IAD → EWR Jul 24, 22:55 UTCJul 25, 00:00 UTC1h 5m
2026-07-24 UAL571 AUS → SFO Jul 24, 19:45 UTCJul 24, 20:55 UTC1h 10m
2026-07-24 UAL520 SFO → JFK Jul 24, 17:10 UTCJul 24, 18:10 UTC1h 0m
2026-07-24 UAL2127 LGA → ORD Jul 24, 13:15 UTCJul 24, 14:20 UTC1h 5m
2026-07-24 UAL2837 NRT → SFO Jul 24, 04:45 UTCJul 24, 06:20 UTC1h 35m
2026-07-24 UAL574K SFO → PHX Jul 24, 00:15 UTCJul 24, 01:50 UTC1h 35m
2026-07-23 UAL1427 MID → IAH Jul 23, 21:15 UTCJul 23, 22:45 UTC1h 30m
2026-07-23 UAL1427 MID → IAH Jul 23, 21:09 UTCJul 23, 22:39 UTC1h 30m
2026-07-23 UAL500 IND → SFO Jul 23, 17:35 UTCJul 23, 19:05 UTC1h 30m
2026-07-23 UAL694 SFO → KOA Jul 23, 12:20 UTCJul 23, 15:25 UTC3h 5m
2026-07-23 UAL1179 IND → IAH Jul 23, 04:45 UTCJul 23, 05:15 UTC30m
2026-07-23 UAL2015 BOS → SFO Jul 23, 00:40 UTCJul 23, 03:30 UTC2h 50m
2026-07-22 UAL1147 SFO → SAN Jul 22, 22:10 UTCJul 22, 23:20 UTC1h 10m
2026-07-22 UAL1333 SNA → ORD Jul 22, 18:45 UTCJul 22, 20:45 UTC2h 0m
2026-07-22 UAL1973 SFO → ORD Jul 22, 04:30 UTCJul 22, 05:25 UTC55m
2026-07-22 UAL1973 SFO → ORD Jul 22, 04:15 UTCJul 22, 06:09 UTC1h 54m
2026-07-22 UAL2841 LAS → SFO Jul 22, 00:30 UTCJul 22, 01:45 UTC1h 15m
2026-07-21 UAL2855 SFO → LAS Jul 21, 21:50 UTCJul 21, 23:05 UTC1h 15m
2026-07-21 UAL1267 EWR → ANC Jul 21, 04:35 UTCJul 21, 05:45 UTC1h 10m
2026-07-21 UAL8123 BOS → YUL Jul 21, 01:10 UTCJul 21, 02:35 UTC1h 25m
2026-07-20 UAL2239 DEN → SFO Jul 20, 19:45 UTCJul 20, 23:40 UTC3h 55m
2026-07-20 UAL2195 ORD → IAH Jul 20, 16:30 UTCJul 20, 18:15 UTC1h 45m
2026-07-20 UAL1811 ORD → BDL Jul 20, 12:15 UTCJul 20, 14:25 UTC2h 10m
2026-07-19 UAL1776 LAX → SFO Jul 19, 23:35 UTCJul 20, 01:10 UTC1h 35m
2026-07-19 UAL2160 PHX → SFO Jul 19, 21:15 UTCJul 19, 21:20 UTC5m
2026-07-19 UAL2160 PHX → SFO Jul 19, 19:30 UTCJul 19, 20:57 UTC1h 27m
2026-07-19 UAL2160 PHX → SFO Jul 19, 19:20 UTCJul 19, 21:20 UTC2h 0m
2026-07-19 UAL441 EWR → FLL Jul 19, 16:05 UTCJul 19, 17:30 UTC1h 25m
2026-07-19 UAL441 EWR → FLL Jul 19, 16:00 UTCJul 19, 17:51 UTC1h 51m
2026-07-19 UAL1733 PDX → SFO Jul 19, 11:35 UTCJul 19, 13:40 UTC2h 5m
2026-07-19 UAL2443 MSN → ORD Jul 19, 00:00 UTCJul 19, 02:25 UTC2h 25m
2026-07-18 UAL1310 EWR → JAX Jul 18, 19:00 UTCJul 18, 21:15 UTC2h 15m
2026-07-17 UAL334 - Jul 17, 22:05 UTCJul 18, 01:20 UTC3h 15m
2026-07-17 UAL334 IAH → LGA Jul 17, 22:01 UTCJul 18, 01:16 UTC3h 15m
2026-07-17 UAL1405 - Jul 17, 18:40 UTCJul 17, 20:35 UTC1h 55m
2026-07-17 UAL1408 - Jul 17, 15:10 UTCJul 17, 16:55 UTC1h 45m
2026-07-17 UAL532 - Jul 17, 11:25 UTCJul 17, 12:55 UTC1h 30m
2026-07-16 UAL8144 - Jul 16, 23:35 UTCJul 17, 01:09 UTC1h 35m
2026-07-16 UAL2457 - Jul 16, 14:50 UTCJul 16, 21:00 UTC6h 10m
2026-07-16 UAL756 - Jul 16, 10:35 UTCJul 16, 13:05 UTC2h 30m

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 N37255 page for operator, model, and routing details .

Mode-S A43E5E frequently asked

What is Mode-S code A43E5E?
A43E5E is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N37255.
Where is Mode-S A43E5E registered?
Mode-S code A43E5E 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 A43E5E broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 20:55 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A43E5E, octal 51037136, decimal 10,763,870.
What flights does A43E5E operate?
Mode-S A43E5E has broadcast 20 distinct callsigns, including UAL520, UAL453, UAL2160, UAL1909, UAL1693.