Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A1BFAC

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N21102 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC.

Hex
A1BFAC
Octal
50337654
Decimal
10,600,364
Country
US
Tail
N21102
Type
B789
No current signal · last broadcast 2h ago
Flights observed
92
Distinct callsigns
12
Country
US
Last broadcast
2h ago

Last known position

Most recent position reported by Mode-S A1BFAC.

Country allocation

The ICAO 24-bit address A1BFAC 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 12 distinct

Callsign Airline Flights Last seen
UAL2 United Airlines 16 2026-05-27
UAL1 United Airlines 16 2026-05-26
UAL382 United Airlines 12 2026-04-26
UAL901 United Airlines 10 2026-05-27
UAL900 United Airlines 10 2026-05-28
UAL1434 United Airlines 8 2026-04-20
UAL2498 United Airlines 7 2026-04-26
UAL755 United Airlines 5 2026-04-19
UAL939 United Airlines 3 2026-05-25
UAL930 United Airlines 3 2026-05-30
UAL1849 United Airlines 1 2026-05-16
UAL1757 United Airlines 1 2026-05-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-05-30 UAL930 SFO → LHR May 30, 03:20 UTCMay 30, 06:05 UTC2h 45m
2026-05-28 UAL900 LHR → SFO May 28, 10:15 UTCMay 28, 20:20 UTC10h 5m
2026-05-27 UAL901 SFO → LHR May 27, 20:35 UTCMay 28, 06:20 UTC9h 45m
2026-05-27 UAL2 SIN → SFO May 27, 02:34 UTCMay 27, 16:10 UTC13h 36m
2026-05-26 UAL1 SFO → SIN May 26, 06:20 UTCMay 26, 22:25 UTC16h 5m
2026-05-25 UAL939 LHR → SFO May 25, 16:00 UTCMay 26, 02:35 UTC10h 34m
2026-05-25 UAL930 SFO → LHR May 25, 03:10 UTCMay 25, 12:55 UTC9h 45m
2026-05-24 UAL900 LHR → SFO May 24, 10:05 UTCMay 24, 20:25 UTC10h 20m
2026-05-23 UAL901 SFO → LHR May 23, 20:30 UTCMay 24, 06:10 UTC9h 40m
2026-05-22 UAL939 LHR → SFO May 22, 16:00 UTCMay 22, 23:00 UTC7h 0m
2026-05-22 UAL939 LHR → SFO May 22, 15:39 UTCMay 23, 01:55 UTC10h 16m
2026-05-22 UAL930 SFO → LHR May 22, 03:25 UTCMay 22, 13:30 UTC10h 4m
2026-05-21 UAL2 SIN → SFO May 21, 02:50 UTCMay 21, 08:00 UTC5h 10m
2026-05-21 UAL2 SIN → SFO May 21, 01:36 UTCMay 21, 16:11 UTC14h 35m
2026-05-20 UAL1 SFO → SIN May 20, 06:36 UTCMay 20, 22:46 UTC16h 10m
2026-05-20 UAL1 SFO → SIN May 20, 06:30 UTCMay 20, 06:55 UTC25m
2026-05-19 UAL900 LHR → SFO May 19, 10:00 UTCMay 19, 10:55 UTC55m
2026-05-19 UAL900 LHR → SFO May 19, 10:00 UTCMay 19, 19:55 UTC9h 55m
2026-05-18 UAL901 SFO → LHR May 18, 20:50 UTCMay 19, 06:30 UTC9h 40m
2026-05-18 UAL2 SIN → SFO May 18, 02:50 UTCMay 18, 04:25 UTC1h 35m
2026-05-17 UAL2 SIN → SFO May 17, 21:05 UTCMay 18, 15:40 UTC18h 35m
2026-05-17 UAL2 SIN → SFO May 17, 20:30 UTCMay 18, 15:40 UTC19h 10m
2026-05-17 UAL1 SFO → SIN May 17, 06:25 UTCMay 17, 21:05 UTC14h 40m
2026-05-17 UAL1 SFO → SIN May 17, 06:11 UTCMay 17, 22:35 UTC16h 24m
2026-05-16 UAL1757 PIT → DEN May 16, 22:35 UTCMay 17, 03:40 UTC5h 5m
2026-05-16 UAL1849 MCO → EWR May 16, 15:50 UTCMay 16, 20:15 UTC4h 25m
2026-05-12 UAL2 SIN → SFO May 12, 02:11 UTCMay 12, 16:51 UTC14h 40m
2026-05-12 UAL2 SIN → SFO May 12, 03:30 UTCMay 12, 16:45 UTC13h 15m
2026-05-11 UAL1 SFO → SIN May 11, 06:27 UTCMay 11, 22:36 UTC16h 9m
2026-05-11 UAL1 SFO → SIN May 11, 06:20 UTCMay 11, 19:45 UTC13h 25m
2026-05-10 UAL900 LHR → SFO May 10, 10:05 UTCMay 10, 20:14 UTC10h 10m
2026-05-09 UAL901 SFO → LHR May 9, 20:15 UTCMay 10, 06:15 UTC10h 0m
2026-05-08 UAL900 LHR → SFO May 8, 10:09 UTCMay 8, 20:35 UTC10h 25m
2026-05-08 UAL900 LHR → SFO May 8, 10:00 UTCMay 8, 20:33 UTC10h 33m
2026-05-07 UAL901 SFO → LHR May 7, 20:17 UTCMay 8, 06:25 UTC10h 8m
2026-05-07 UAL901 SFO → LHR May 7, 20:35 UTCMay 8, 06:25 UTC9h 50m
2026-05-07 UAL2 SIN → SFO May 7, 01:31 UTCMay 7, 16:24 UTC14h 53m
2026-05-06 UAL2 SIN → SFO May 6, 20:55 UTCMay 7, 16:25 UTC19h 30m
2026-05-06 UAL1 SFO → SIN May 6, 06:25 UTCMay 7, 04:40 UTC22h 15m
2026-05-05 UAL900 LHR → SFO May 5, 09:50 UTCMay 5, 19:50 UTC10h 0m
2026-05-05 UAL900 LHR → SFO May 5, 10:00 UTCMay 5, 19:45 UTC9h 45m
2026-05-04 UAL901 SFO → LHR May 4, 20:17 UTCMay 5, 06:09 UTC9h 52m
2026-05-04 UAL901 SFO → LHR May 4, 20:15 UTCMay 5, 06:15 UTC10h 0m
2026-05-04 UAL2 SIN → SFO May 4, 02:35 UTCMay 4, 16:15 UTC13h 40m
2026-05-03 UAL1 SFO → SIN May 3, 22:25 UTCMay 3, 22:34 UTC10m
2026-05-03 UAL1 SFO → SIN May 3, 06:20 UTCMay 3, 21:10 UTC14h 50m
2026-05-02 UAL900 LHR → SFO May 2, 09:55 UTCMay 2, 20:35 UTC10h 40m
2026-05-01 UAL901 SFO → LHR May 1, 20:40 UTCMay 2, 06:20 UTC9h 41m
2026-05-01 UAL901 SFO → LHR May 1, 20:22 UTCMay 2, 06:17 UTC9h 55m
2026-05-01 UAL2 SIN → SFO May 1, 16:20 UTCMay 1, 16:25 UTC5m

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 N21102 page for operator, model, and routing details .

Mode-S A1BFAC frequently asked

What is Mode-S code A1BFAC?
A1BFAC is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N21102.
Where is Mode-S A1BFAC registered?
Mode-S code A1BFAC 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 A1BFAC broadcasting right now?
No active broadcast right now. Last signal was 2h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1BFAC, octal 50337654, decimal 10,600,364.
What flights does A1BFAC operate?
Mode-S A1BFAC has broadcast 12 distinct callsigns, including UAL2, UAL1, UAL382, UAL901, UAL900.