Apparatus

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sensors Mode-S transponder

A3EFA2

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N35271 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
A3EFA2
Octal
50767642
Decimal
10,743,714
Country
US
Tail
N35271
Type
B738
Broadcasting now · callsign UAL1989 · 25,500 ft
Flights observed
407
Distinct callsigns
20
Country
US
Last broadcast
24m ago

Current position

A3EFA2 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A3EFA2 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
UAL763 United Airlines 4 2026-06-26
UAL590 - 4 2026-06-29
UAL582 - 4 2026-07-05
UAL547 - 4 2026-06-12
UAL2487 United Airlines 4 2026-06-10
UAL1737 - 4 2026-06-28
UAL1677 United Airlines 4 2026-05-23
UAL586 United Airlines 3 2026-05-27
UAL493 United Airlines 3 2026-06-04
UAL425 United Airlines 3 2026-04-19
UAL401 - 3 2026-06-28
UAL3882 - 3 2026-07-11
UAL2668 - 3 2026-06-26
UAL2644 United Airlines 3 2026-05-04
UAL244 United Airlines 3 2026-06-07
UAL2411 - 3 2026-04-13
UAL2371 United Airlines 3 2026-04-15
UAL2306 United Airlines 3 2026-05-26
UAL2272 United Airlines 3 2026-05-01
UAL2239 United Airlines 3 2026-05-30

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 UAL1989 - Jul 14, 01:40 UTCJul 14, 02:30 UTC50m
2026-07-13 UAL602 LGA → ORD Jul 13, 21:35 UTCJul 13, 23:30 UTC1h 55m
2026-07-13 UAL2189 ORD → LGA Jul 13, 18:15 UTCJul 13, 19:55 UTC1h 40m
2026-07-13 UAL1310 LGA → ORD Jul 13, 14:30 UTCJul 13, 16:15 UTC1h 45m
2026-07-13 UAL2617 ORD → LGA Jul 13, 11:40 UTCJul 13, 13:20 UTC1h 40m
2026-07-13 UAL249 YVR → ORD Jul 13, 06:50 UTCJul 13, 10:15 UTC3h 25m
2026-07-13 UAL1580 ORD → YVR Jul 13, 01:22 UTCJul 13, 05:14 UTC3h 52m
2026-07-13 UAL1580 ORD → YVR Jul 13, 01:20 UTCJul 13, 05:20 UTC4h 0m
2026-07-12 UAL433 - Jul 12, 20:40 UTCJul 12, 22:20 UTC1h 40m
2026-07-12 UAL433 ALB → ORD Jul 12, 20:40 UTCJul 12, 22:03 UTC1h 23m
2026-07-12 UAL1554 ORD → ALB Jul 12, 17:15 UTCJul 12, 18:45 UTC1h 30m
2026-07-12 UAL1057 LGA → ORD Jul 12, 13:25 UTCJul 12, 15:35 UTC2h 10m
2026-07-11 UAL2809 ORD → LGA Jul 11, 22:38 UTCJul 12, 00:13 UTC1h 35m
2026-07-11 UAL2809 ORD → LGA Jul 11, 22:35 UTCJul 12, 00:15 UTC1h 40m
2026-07-11 UAL456 AUS → ORD Jul 11, 18:40 UTCJul 11, 20:50 UTC2h 10m
2026-07-11 UAL1688 ORD → AUS Jul 11, 14:38 UTCJul 11, 16:48 UTC2h 10m
2026-07-11 UAL1688 ORD → AUS Jul 11, 14:40 UTCJul 11, 16:50 UTC2h 10m
2026-07-11 UAL490 - Jul 11, 11:25 UTCJul 11, 12:30 UTC1h 5m
2026-07-11 UAL3882 - Jul 11, 06:15 UTCJul 11, 07:50 UTC1h 35m
2026-07-07 UAL3882 IAD → IAB Jul 7, 04:45 UTCJul 7, 06:58 UTC2h 13m
2026-07-07 UAL3882 IAD → CEA Jul 7, 04:40 UTCJul 7, 06:55 UTC2h 15m
2026-07-06 UAL2131 SEA → IAD Jul 6, 20:20 UTCJul 7, 00:55 UTC4h 35m
2026-07-06 UAL2101 IAD → SEA Jul 6, 13:35 UTCJul 6, 18:40 UTC5h 5m
2026-07-05 UAL1140 LAS → IAD Jul 5, 16:00 UTCJul 5, 20:15 UTC4h 15m
2026-07-05 UAL582 - Jul 5, 13:05 UTCJul 5, 14:15 UTC1h 10m
2026-07-05 UAL582 SFO → LAS Jul 5, 13:19 UTCJul 5, 14:13 UTC54m
2026-07-05 UAL2216 YVR → SFO Jul 5, 00:43 UTCJul 5, 02:45 UTC2h 2m
2026-07-05 UAL2216 YVR → SFO Jul 5, 00:35 UTCJul 5, 02:30 UTC1h 55m
2026-07-04 UAL1151 - Jul 4, 21:20 UTCJul 4, 23:10 UTC1h 50m
2026-07-04 UAL2386 BUR → SFO Jul 4, 18:20 UTCJul 4, 19:15 UTC55m
2026-07-04 UAL2363 - Jul 4, 16:05 UTCJul 4, 17:00 UTC55m
2026-07-03 UAL1896 - Jul 3, 12:20 UTCJul 3, 13:40 UTC1h 20m
2026-07-03 UAL1770 DEN → PDX Jul 3, 05:05 UTCJul 3, 07:20 UTC2h 15m
2026-07-03 UAL1924 YYC → DEN Jul 3, 02:00 UTCJul 3, 03:55 UTC1h 55m
2026-07-02 UAL2232 - Jul 2, 22:50 UTCJul 3, 00:50 UTC2h 0m
2026-07-02 UAL708 - Jul 2, 19:20 UTCJul 2, 20:55 UTC1h 35m
2026-07-02 UAL708 MCI → DEN Jul 2, 19:19 UTCJul 2, 20:50 UTC1h 31m
2026-07-02 UAL2159 - Jul 2, 16:00 UTCJul 2, 17:10 UTC1h 10m
2026-07-02 UAL2754 - Jul 2, 12:10 UTCJul 2, 14:10 UTC2h 0m
2026-07-02 UAL1371 SNA → ORD Jul 2, 02:05 UTCJul 2, 04:20 UTC2h 15m
2026-07-01 UAL1001 - Jul 1, 20:30 UTCJul 1, 23:15 UTC2h 45m
2026-07-01 UAL1001 PNS → DEN Jul 1, 20:42 UTCJul 1, 23:09 UTC2h 27m
2026-07-01 UAL2185 - Jul 1, 16:40 UTCJul 1, 19:00 UTC2h 20m
2026-07-01 UAL1877 - Jul 1, 13:15 UTCJul 1, 13:55 UTC40m
2026-07-01 UAL431 - Jul 1, 03:10 UTCJul 1, 03:45 UTC35m
2026-07-01 UAL1303 EWR → IAH Jul 1, 00:15 UTCJul 1, 01:50 UTC1h 35m
2026-06-30 UAL2290 - Jun 30, 19:10 UTCJun 30, 20:55 UTC1h 45m
2026-06-30 UAL1968 YYC → ORD Jun 30, 14:49 UTCJun 30, 17:17 UTC2h 28m
2026-06-30 UAL1968 - Jun 30, 14:40 UTCJun 30, 17:30 UTC2h 50m
2026-06-30 UAL1156 - Jun 30, 01:30 UTCJun 30, 04:45 UTC3h 15m

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 N35271 page for operator, model, and routing details .

Mode-S A3EFA2 frequently asked

What is Mode-S code A3EFA2?
A3EFA2 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N35271.
Where is Mode-S A3EFA2 registered?
Mode-S code A3EFA2 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 A3EFA2 broadcasting right now?
Yes. Mode-S A3EFA2 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A3EFA2, octal 50767642, decimal 10,743,714.
What flights does A3EFA2 operate?
Mode-S A3EFA2 has broadcast 20 distinct callsigns, including UAL763, UAL590, UAL582, UAL547, UAL2487.