Apparatus

Try JFK, AAL1290, BAW, or N225AN.

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
No current signal · last broadcast Jul 26, 22:05 UTC
Flights observed
475
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:05 UTC

Last known position

Most recent position reported by Mode-S A3EFA2.

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
UAL582 - 5 2026-07-16
UAL2239 United Airlines 5 2026-07-21
UAL763 United Airlines 4 2026-06-26
UAL590 - 4 2026-06-29
UAL547 - 4 2026-06-12
UAL500 United Airlines 4 2026-07-23
UAL2487 United Airlines 4 2026-06-10
UAL2195 United Airlines 4 2026-07-21
UAL1737 - 4 2026-06-28
UAL1677 United Airlines 4 2026-05-23
UAL1427 - 4 2026-07-15
UAL586 United Airlines 3 2026-05-27
UAL571 - 3 2026-07-15
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

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1911 IAD → EWR Jul 26, 21:55 UTCJul 26, 22:05 UTC10m
2026-07-26 UAL275 EWR → SFO Jul 26, 20:15 UTCJul 26, 20:25 UTC10m
2026-07-26 UAL275 EWR → SFO Jul 26, 18:00 UTCJul 26, 18:30 UTC30m
2026-07-26 UAL251 BWI → LAX Jul 26, 14:10 UTCJul 26, 16:00 UTC1h 50m
2026-07-26 UAL1381 IAH → SAN Jul 26, 02:05 UTCJul 26, 03:40 UTC1h 35m
2026-07-26 UAL1381 IAH → SAN Jul 26, 01:57 UTCJul 26, 03:37 UTC1h 40m
2026-07-25 UAL1976 BOS → IAH Jul 25, 18:20 UTCJul 25, 21:55 UTC3h 35m
2026-07-25 UAL1977 LAX → SFO Jul 25, 13:30 UTCJul 25, 16:40 UTC3h 10m
2026-07-25 UAL631 IAH → BWI Jul 25, 08:00 UTCJul 25, 12:00 UTC4h 0m
2026-07-25 UAL1359 IAH → EWR Jul 25, 01:35 UTCJul 25, 05:50 UTC4h 15m
2026-07-24 UAL1834 DFW → EWR Jul 24, 21:35 UTCJul 24, 23:25 UTC1h 50m
2026-07-24 UAL1501 EWR → SFO Jul 24, 18:15 UTCJul 24, 20:00 UTC1h 45m
2026-07-24 UAL2760 VCV → SFO Jul 24, 13:50 UTCJul 24, 16:35 UTC2h 45m
2026-07-24 UAL8284 DEN → CID Jul 24, 05:48 UTCJul 24, 06:59 UTC1h 11m
2026-07-24 UAL8284 DEN → CID Jul 24, 05:55 UTCJul 24, 07:05 UTC1h 10m
2026-07-23 UAL285 BUF → EWR Jul 23, 23:50 UTCJul 24, 04:25 UTC4h 35m
2026-07-23 UAL702 EWR → IAH Jul 23, 16:30 UTCJul 23, 20:40 UTC4h 10m
2026-07-23 UAL500 IND → SFO Jul 23, 10:25 UTCJul 23, 14:35 UTC4h 10m
2026-07-23 UAL1199 EWR → CLT Jul 23, 00:40 UTCJul 23, 02:45 UTC2h 5m
2026-07-22 UAL302 - Jul 22, 19:40 UTCJul 22, 22:45 UTC3h 5m
2026-07-22 UAL1915 SAN → SFO Jul 22, 15:50 UTCJul 22, 18:15 UTC2h 25m
2026-07-22 UAL1915 SAN → SFO Jul 22, 15:56 UTCJul 22, 18:10 UTC2h 14m
2026-07-22 UAL687 EWR → IAH Jul 22, 13:15 UTCJul 22, 13:55 UTC40m
2026-07-22 UAL1390 LAS → EWR Jul 22, 02:25 UTCJul 22, 03:00 UTC35m
2026-07-22 UAL1390 LAS → EWR Jul 22, 02:11 UTCJul 22, 03:07 UTC56m
2026-07-21 UAL2239 DEN → SFO Jul 21, 21:05 UTCJul 22, 00:30 UTC3h 25m
2026-07-21 UAL2239 DEN → SFO Jul 21, 21:05 UTCJul 22, 00:58 UTC3h 53m
2026-07-21 UAL2195 ORD → IAH Jul 21, 16:40 UTCJul 21, 18:20 UTC1h 40m
2026-07-21 UAL2151 PDX → DEN Jul 21, 13:30 UTCJul 21, 14:00 UTC30m
2026-07-21 UAL2151 PDX → DEN Jul 21, 13:37 UTCJul 21, 13:48 UTC11m
2026-07-21 UAL630 BUF → ORD Jul 21, 03:35 UTCJul 21, 04:05 UTC30m
2026-07-20 UAL2797 - Jul 20, 23:20 UTCJul 21, 01:05 UTC1h 44m
2026-07-20 UAL2430 ORD → ALB Jul 20, 20:15 UTCJul 20, 21:45 UTC1h 30m
2026-07-20 UAL2207 ORD → PIT Jul 20, 15:40 UTCJul 20, 17:30 UTC1h 50m
2026-07-20 UAL2038 - Jul 20, 12:40 UTCJul 20, 14:10 UTC1h 30m
2026-07-20 UAL2038 ORD → PHL Jul 20, 12:48 UTCJul 20, 14:07 UTC1h 19m
2026-07-20 UAL1621 LAX → MCO Jul 20, 00:25 UTCJul 20, 02:45 UTC2h 20m
2026-07-19 UAL1811 ORD → BDL Jul 19, 18:30 UTCJul 19, 20:40 UTC2h 10m
2026-07-19 UAL1502 EWR → ORD Jul 19, 14:15 UTCJul 19, 17:05 UTC2h 50m
2026-07-19 UAL1710 SAN → ORD Jul 19, 03:28 UTCJul 19, 06:03 UTC2h 35m
2026-07-19 UAL1710 ORD → SLC Jul 19, 03:20 UTCJul 19, 06:00 UTC2h 40m
2026-07-18 UAL2628 PHL → IAH Jul 18, 21:55 UTCJul 19, 01:00 UTC3h 5m
2026-07-18 UAL2822 - Jul 18, 16:40 UTCJul 18, 19:35 UTC2h 55m
2026-07-18 UAL623 LGA → ORD Jul 18, 12:40 UTCJul 18, 14:45 UTC2h 5m
2026-07-18 UAL623 LGA → ORD Jul 18, 12:26 UTCJul 18, 14:29 UTC2h 3m
2026-07-18 UAL2267 EWR → RDU Jul 18, 01:39 UTCJul 18, 03:20 UTC1h 41m
2026-07-18 UAL2267 EWR → RDU Jul 18, 01:34 UTCJul 18, 03:22 UTC1h 48m
2026-07-17 UAL202 - Jul 17, 22:29 UTCJul 17, 23:00 UTC30m
2026-07-17 UAL202 MKE → ORD Jul 17, 22:07 UTCJul 17, 22:48 UTC41m
2026-07-17 UAL202 AUS → MKE Jul 17, 15:40 UTCJul 17, 18:40 UTC3h 0m

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?
No active broadcast right now. Last signal was Jul 26, 22:05 UTC.
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 UAL582, UAL2239, UAL763, UAL590, UAL547.