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
Broadcasting now · callsign UAL900 · 10,050 ft
Flights observed
170
Distinct callsigns
18
Country
US
Last broadcast
5h ago

Current position

A1BFAC is currently broadcasting. Map zoomed to live position.

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 18 distinct

Callsign Airline Flights Last seen
UAL2 - 29 2026-07-13
UAL1 - 27 2026-07-12
UAL901 - 24 2026-07-13
UAL900 - 23 2026-07-11
UAL930 - 14 2026-07-09
UAL939 - 13 2026-07-09
UAL382 United Airlines 12 2026-04-26
UAL1434 United Airlines 8 2026-04-20
UAL2498 United Airlines 7 2026-04-26
UAL755 United Airlines 5 2026-04-19
UAL949 - 1 2026-07-03
UAL948 - 1 2026-07-03
UAL3920 - 1 2026-06-29
UAL3888 - 1 2026-06-28
UAL345 United Airlines 1 2026-06-28
UAL344 United Airlines 1 2026-06-29
UAL1849 United Airlines 1 2026-05-16
UAL1757 United Airlines 1 2026-05-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-13 UAL901 SFO → LHR Jul 13, 20:27 UTCJul 14, 05:42 UTC9h 15m
2026-07-13 UAL901 SFO → LHR Jul 13, 20:20 UTCJul 14, 05:40 UTC9h 20m
2026-07-13 UAL2 - Jul 13, 02:35 UTCJul 13, 16:40 UTC14h 5m
2026-07-13 UAL2 - Jul 13, 01:15 UTCJul 13, 01:25 UTC10m
2026-07-12 UAL1 - Jul 12, 22:05 UTCJul 12, 22:15 UTC10m
2026-07-12 UAL1 - Jul 12, 06:30 UTCJul 12, 20:50 UTC14h 20m
2026-07-11 UAL900 - Jul 11, 10:10 UTCJul 11, 20:30 UTC10h 20m
2026-07-10 UAL901 SFO → LHR Jul 10, 20:40 UTCJul 11, 06:25 UTC9h 45m
2026-07-09 UAL939 - Jul 9, 15:40 UTCJul 10, 02:00 UTC10h 20m
2026-07-09 UAL930 SFO → LHR Jul 9, 03:19 UTCJul 9, 12:51 UTC9h 32m
2026-07-09 UAL930 SFO → LHR Jul 9, 03:10 UTCJul 9, 12:55 UTC9h 45m
2026-07-08 UAL900 - Jul 8, 09:55 UTCJul 8, 20:10 UTC10h 15m
2026-07-07 UAL901 SFO → LHR Jul 7, 20:45 UTCJul 8, 06:20 UTC9h 35m
2026-07-06 UAL900 - Jul 6, 10:00 UTCJul 6, 20:30 UTC10h 30m
2026-07-05 UAL901 SFO → LHR Jul 5, 20:35 UTCJul 6, 06:15 UTC9h 40m
2026-07-05 UAL2 - Jul 5, 03:00 UTCJul 5, 16:40 UTC13h 40m
2026-07-04 UAL1 SFO → SIN Jul 4, 06:21 UTCJul 4, 21:51 UTC15h 30m
2026-07-04 UAL1 - Jul 4, 06:25 UTCJul 4, 06:55 UTC30m
2026-07-03 UAL949 - Jul 3, 12:25 UTCJul 3, 22:35 UTC10h 10m
2026-07-03 UAL948 SFO → LHR Jul 3, 00:15 UTCJul 3, 09:40 UTC9h 25m
2026-07-02 UAL900 - Jul 2, 10:00 UTCJul 2, 20:10 UTC10h 10m
2026-07-02 UAL900 LHR → SFO Jul 2, 10:00 UTCJul 2, 20:06 UTC10h 6m
2026-07-01 UAL901 SFO → LHR Jul 1, 20:20 UTCJul 2, 05:50 UTC9h 30m
2026-06-30 UAL939 - Jun 30, 16:00 UTCJul 1, 02:00 UTC10h 0m
2026-06-30 UAL930 SFO → LHR Jun 30, 03:19 UTCJun 30, 13:19 UTC10h 0m
2026-06-30 UAL930 SFO → LHR Jun 30, 03:45 UTCJun 30, 13:00 UTC9h 15m
2026-06-29 UAL3920 IAD → SFO Jun 29, 12:05 UTCJun 29, 16:59 UTC4h 55m
2026-06-29 UAL344 HNL → IAD Jun 29, 01:50 UTCJun 29, 10:15 UTC8h 25m
2026-06-28 UAL345 IAD → HNL Jun 28, 13:34 UTCJun 28, 22:59 UTC9h 25m
2026-06-28 UAL3888 - Jun 28, 06:05 UTCJun 28, 10:15 UTC4h 10m
2026-06-27 UAL939 - Jun 27, 15:55 UTCJun 28, 02:05 UTC10h 10m
2026-06-27 UAL930 SFO → LHR Jun 27, 03:30 UTCJun 27, 13:24 UTC9h 54m
2026-06-27 UAL930 SFO → LHR Jun 27, 03:34 UTCJun 27, 13:00 UTC9h 25m
2026-06-25 UAL939 - Jun 25, 15:54 UTCJun 26, 01:54 UTC10h 0m
2026-06-25 UAL930 SFO → LHR Jun 25, 03:40 UTCJun 25, 13:24 UTC9h 45m
2026-06-23 UAL900 - Jun 23, 10:24 UTCJun 23, 20:40 UTC10h 15m
2026-06-22 UAL901 SFO → LHR Jun 22, 20:44 UTCJun 23, 06:29 UTC9h 45m
2026-06-22 UAL2 - Jun 22, 04:09 UTCJun 22, 15:35 UTC11h 25m
2026-06-21 UAL1 - Jun 21, 06:35 UTCJun 21, 22:15 UTC15h 40m
2026-06-20 UAL900 - Jun 20, 09:59 UTCJun 20, 20:00 UTC10h 0m
2026-06-19 UAL901 SFO → LHR Jun 19, 20:40 UTCJun 20, 06:10 UTC9h 30m
2026-06-18 UAL939 - Jun 18, 15:45 UTCJun 19, 01:45 UTC9h 59m
2026-06-18 UAL930 SFO → LHR Jun 18, 03:20 UTCJun 18, 13:10 UTC9h 50m
2026-06-17 UAL2 - Jun 17, 02:55 UTCJun 17, 16:35 UTC13h 40m
2026-06-16 UAL1 - Jun 16, 06:35 UTCJun 16, 20:45 UTC14h 11m
2026-06-16 UAL1 SFO → SIN Jun 16, 06:36 UTCJun 16, 22:12 UTC15h 36m
2026-06-15 UAL939 - Jun 15, 15:55 UTCJun 16, 01:35 UTC9h 40m
2026-06-15 UAL930 SFO → LHR Jun 15, 03:19 UTCJun 15, 13:01 UTC9h 42m
2026-06-15 UAL930 SFO → LHR Jun 15, 03:15 UTCJun 15, 13:00 UTC9h 45m
2026-06-14 UAL900 - Jun 14, 09:50 UTCJun 14, 19:45 UTC9h 55m

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?
Yes. Mode-S A1BFAC is currently airborne.
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 18 distinct callsigns, including UAL2, UAL1, UAL901, UAL900, UAL930.