Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A3EF1B

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N35236 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
A3EF1B
Octal
50767433
Decimal
10,743,579
Country
US
Tail
N35236
Type
B738
No current signal · last broadcast 6d ago
Flights observed
409
Distinct callsigns
20
Country
US
Last broadcast
6d ago

Last known position

Most recent position reported by Mode-S A3EF1B.

Country allocation

The ICAO 24-bit address A3EF1B 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
UAL2745 - 5 2026-06-27
UAL1191 United Airlines 5 2026-07-20
UAL590 - 4 2026-07-04
UAL2644 - 4 2026-07-15
UAL2257 - 4 2026-07-16
UAL1787 United Airlines 4 2026-05-23
UAL1622 - 4 2026-06-23
UAL1318 - 4 2026-06-20
UAL1315 United Airlines 4 2026-06-01
UAL1022 United Airlines 4 2026-06-01
UAL704 - 3 2026-07-05
UAL550 United Airlines 3 2026-07-19
UAL503 - 3 2026-07-05
UAL401 - 3 2026-06-22
UAL345 United Airlines 3 2026-05-21
UAL296 United Airlines 3 2026-07-19
UAL275 - 3 2026-06-19
UAL2456 - 3 2026-06-13
UAL2432 United Airlines 3 2026-06-20
UAL2323 United Airlines 3 2026-06-01

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL452 SFO → ORD Jul 26, 17:45 UTCJul 26, 18:45 UTC1h 0m
2026-07-26 UAL671 DEN → BZN Jul 26, 12:15 UTCJul 26, 15:10 UTC2h 55m
2026-07-26 UAL671 DEN → BZN Jul 26, 12:21 UTCJul 26, 15:07 UTC2h 46m
2026-07-25 UAL1485 DEN → SFO Jul 25, 22:30 UTCJul 26, 01:25 UTC2h 55m
2026-07-25 UAL1485 DEN → SFO Jul 25, 22:28 UTCJul 26, 01:26 UTC2h 58m
2026-07-25 UAL1788 SFO → IAH Jul 25, 20:05 UTCJul 25, 20:40 UTC35m
2026-07-25 UAL1714 LAS → IAH Jul 25, 18:00 UTCJul 25, 18:20 UTC20m
2026-07-25 UAL2789 GUM → SFO Jul 25, 15:30 UTCJul 25, 16:30 UTC1h 0m
2026-07-25 UAL2166 TPA → SFO Jul 25, 03:20 UTCJul 25, 04:15 UTC55m
2026-07-25 UAL2108 EWR → CHS Jul 25, 00:00 UTCJul 25, 01:40 UTC1h 40m
2026-07-24 UAL2156 IAH → SFO Jul 24, 17:45 UTCJul 24, 22:10 UTC4h 25m
2026-07-24 UAL2098 BOS → IAD Jul 24, 13:35 UTCJul 24, 14:50 UTC1h 15m
2026-07-23 UAL2798 MIA → ORD Jul 23, 22:20 UTCJul 24, 01:40 UTC3h 20m
2026-07-23 UAL1396 RSW → EWR Jul 23, 20:15 UTCJul 23, 21:00 UTC45m
2026-07-23 UAL1217 IAH → BOS Jul 23, 18:10 UTCJul 23, 18:40 UTC30m
2026-07-23 UAL2750 PVR → SFO Jul 23, 12:05 UTCJul 23, 15:45 UTC3h 40m
2026-07-23 UAL8216 PDX → YVR Jul 23, 04:00 UTCJul 23, 07:00 UTC3h 0m
2026-07-23 UAL478 DEN → ORD Jul 23, 01:35 UTCJul 23, 02:45 UTC1h 10m
2026-07-22 UAL703 DEN → BIL Jul 22, 18:05 UTCJul 22, 19:05 UTC1h 0m
2026-07-22 UAL1727 LAS → SFO Jul 22, 13:30 UTCJul 22, 16:50 UTC3h 20m
2026-07-22 UAL248 BOS → IAH Jul 22, 00:15 UTCJul 22, 02:50 UTC2h 35m
2026-07-21 UAL2173 MYR → ORD Jul 21, 20:45 UTCJul 21, 22:15 UTC1h 30m
2026-07-21 UAL2255 MSO → DEN Jul 21, 17:50 UTCJul 21, 19:15 UTC1h 25m
2026-07-21 UAL2789 GUM → SFO Jul 21, 15:05 UTCJul 21, 16:15 UTC1h 10m
2026-07-21 UAL2166 DEN → ICT Jul 21, 01:05 UTCJul 21, 02:05 UTC1h 0m
2026-07-20 UAL725 ORD → SFO Jul 20, 22:35 UTCJul 20, 23:35 UTC1h 0m
2026-07-20 UAL691 ORD → IAH Jul 20, 20:35 UTCJul 20, 21:25 UTC50m
2026-07-20 UAL691 ORD → IAH Jul 20, 20:34 UTCJul 20, 21:26 UTC52m
2026-07-20 UAL1191 COS → DEN Jul 20, 16:20 UTCJul 20, 18:20 UTC2h 0m
2026-07-20 UAL1191 COS → DEN Jul 20, 16:23 UTCJul 20, 18:15 UTC1h 52m
2026-07-20 UAL689 IAD → MCO Jul 20, 13:55 UTCJul 20, 14:45 UTC50m
2026-07-20 UAL2615 LAS → SFO Jul 20, 05:15 UTCJul 20, 06:15 UTC1h 0m
2026-07-20 UAL2615 LAS → SFO Jul 20, 04:54 UTCJul 20, 06:14 UTC1h 20m
2026-07-20 UAL655 DEN → LAS Jul 20, 02:10 UTCJul 20, 03:35 UTC1h 25m
2026-07-19 UAL296 ORD → FSD Jul 19, 15:50 UTCJul 19, 22:50 UTC7h 0m
2026-07-19 UAL550 DEN → DFW Jul 19, 12:22 UTCJul 19, 14:11 UTC1h 49m
2026-07-19 UAL550 DEN → DFW Jul 19, 12:15 UTCJul 19, 14:15 UTC2h 0m
2026-07-19 UAL720 DEN → YYC Jul 19, 01:40 UTCJul 19, 03:40 UTC2h 0m
2026-07-18 UAL2085 EWR → AUS Jul 18, 21:35 UTCJul 18, 23:55 UTC2h 20m
2026-07-18 UAL8151 YYZ → DTW Jul 18, 18:13 UTCJul 18, 20:05 UTC1h 52m
2026-07-18 UAL8151 YYZ → DTW Jul 18, 18:25 UTCJul 18, 20:05 UTC1h 40m
2026-07-18 UAL500 IND → SFO Jul 18, 12:30 UTCJul 18, 16:30 UTC4h 0m
2026-07-18 UAL1199 EWR → CLT Jul 18, 00:45 UTCJul 18, 02:40 UTC1h 55m
2026-07-17 UAL302 - Jul 17, 20:44 UTCJul 17, 23:10 UTC2h 25m
2026-07-17 UAL1915 SAN → SFO Jul 17, 16:44 UTCJul 17, 19:05 UTC2h 20m
2026-07-17 UAL687 - Jul 17, 13:25 UTCJul 17, 14:10 UTC45m
2026-07-17 UAL1390 - Jul 17, 01:25 UTCJul 17, 01:59 UTC35m
2026-07-16 UAL296 ORD → FSD Jul 16, 21:19 UTCJul 16, 23:05 UTC1h 45m
2026-07-16 UAL2257 DEN → PVR Jul 16, 15:56 UTCJul 16, 18:28 UTC2h 32m
2026-07-16 UAL2257 - Jul 16, 15:49 UTCJul 16, 16:55 UTC1h 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 N35236 page for operator, model, and routing details .

Mode-S A3EF1B frequently asked

What is Mode-S code A3EF1B?
A3EF1B is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N35236.
Where is Mode-S A3EF1B registered?
Mode-S code A3EF1B 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 A3EF1B broadcasting right now?
No active broadcast right now. Last signal was 6d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A3EF1B, octal 50767433, decimal 10,743,579.
What flights does A3EF1B operate?
Mode-S A3EF1B has broadcast 20 distinct callsigns, including UAL2745, UAL1191, UAL590, UAL2644, UAL2257.