Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A6679B

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N51104 · BOEING 787-9 Dreamliner · operated by UNITED AIRLINES INC.

Hex
A6679B
Octal
51463633
Decimal
10,905,499
Country
US
Tail
N51104
Type
B789
No current signal · last broadcast Jul 26, 16:40 UTC
Flights observed
171
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 16:40 UTC

Last known position

Most recent position reported by Mode-S A6679B.

Country allocation

The ICAO 24-bit address A6679B 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
UAL1 United Airlines 34 2026-07-23
UAL2 United Airlines 27 2026-07-24
UAL900 United Airlines 21 2026-07-21
UAL901 - 20 2026-07-20
UAL930 - 18 2026-07-22
UAL939 United Airlines 15 2026-07-22
UAL755 United Airlines 7 2026-04-17
UAL2498 United Airlines 7 2026-04-27
UAL382 United Airlines 6 2026-04-27
UAL1434 United Airlines 5 2026-04-18
UAL3867 United Airlines 2 2026-06-14
UAL505 United Airlines 1 2026-04-30
UAL3974 United Airlines 1 2026-05-14
UAL3968 United Airlines 1 2026-06-10
UAL3932 United Airlines 1 2026-05-14
UAL29 United Airlines 1 2026-07-25
UAL28 United Airlines 1 2026-07-26
UAL2633 United Airlines 1 2026-07-25
UAL1768 United Airlines 1 2026-04-30
UAL1604 United Airlines 1 2026-07-24

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL28 SIN → SFO Jul 26, 14:40 UTCJul 26, 16:40 UTC2h 0m
2026-07-25 UAL29 SFO → SIN Jul 25, 19:10 UTCJul 26, 08:50 UTC13h 41m
2026-07-25 UAL2633 PHL → IAH Jul 25, 01:10 UTCJul 25, 03:35 UTC2h 25m
2026-07-24 UAL1604 SFO → BNA Jul 24, 21:20 UTCJul 24, 23:15 UTC1h 55m
2026-07-24 UAL2 SIN → SFO Jul 24, 01:10 UTCJul 24, 16:20 UTC15h 10m
2026-07-23 UAL1 SFO → SIN Jul 23, 21:45 UTCJul 23, 22:05 UTC20m
2026-07-23 UAL1 SFO → SIN Jul 23, 06:35 UTCJul 23, 19:20 UTC12h 45m
2026-07-22 UAL939 LHR → SFO Jul 22, 16:10 UTCJul 23, 02:20 UTC10h 10m
2026-07-22 UAL930 SFO → LHR Jul 22, 03:15 UTCJul 22, 12:55 UTC9h 40m
2026-07-21 UAL900 LHR → SFO Jul 21, 10:20 UTCJul 21, 20:35 UTC10h 15m
2026-07-20 UAL901 SFO → LHR Jul 20, 20:40 UTCJul 21, 06:15 UTC9h 35m
2026-07-20 UAL2 SIN → SFO Jul 20, 03:55 UTCJul 20, 16:00 UTC12h 5m
2026-07-20 UAL2 SIN → SFO Jul 20, 01:16 UTCJul 20, 15:54 UTC14h 38m
2026-07-19 UAL1 SFO → SIN Jul 19, 06:26 UTCJul 19, 22:00 UTC15h 34m
2026-07-19 UAL1 SFO → SIN Jul 19, 06:25 UTCJul 19, 20:35 UTC14h 10m
2026-07-17 UAL939 - Jul 17, 15:25 UTCJul 18, 01:34 UTC10h 10m
2026-07-17 UAL930 - Jul 17, 03:14 UTCJul 17, 12:50 UTC9h 35m
2026-07-16 UAL900 - Jul 16, 10:04 UTCJul 16, 20:29 UTC10h 25m
2026-07-16 UAL900 LHR → SFO Jul 16, 10:00 UTCJul 16, 20:25 UTC10h 25m
2026-07-15 UAL901 SFO → LHR Jul 15, 20:25 UTCJul 16, 05:55 UTC9h 30m
2026-07-15 UAL2 - Jul 15, 02:30 UTCJul 15, 15:55 UTC13h 25m
2026-07-15 UAL2 SIN → SFO Jul 15, 01:16 UTCJul 15, 16:00 UTC14h 44m
2026-07-14 UAL1 - Jul 14, 21:45 UTCJul 14, 21:55 UTC10m
2026-07-14 UAL1 - Jul 14, 06:30 UTCJul 14, 20:40 UTC14h 10m
2026-07-13 UAL939 - Jul 13, 17:05 UTCJul 14, 03:45 UTC10h 40m
2026-07-13 UAL939 LHR → SFO Jul 13, 15:39 UTCJul 14, 03:41 UTC12h 2m
2026-07-13 UAL930 SFO → LHR Jul 13, 03:15 UTCJul 13, 12:55 UTC9h 40m
2026-07-11 UAL939 LHR → SFO Jul 11, 15:55 UTCJul 12, 02:20 UTC10h 25m
2026-07-11 UAL930 SFO → LHR Jul 11, 03:10 UTCJul 11, 12:45 UTC9h 35m
2026-07-10 UAL900 - Jul 10, 10:15 UTCJul 10, 20:40 UTC10h 25m
2026-07-09 UAL901 SFO → LHR Jul 9, 20:20 UTCJul 10, 06:10 UTC9h 50m
2026-07-08 UAL939 - Jul 8, 15:40 UTCJul 9, 01:45 UTC10h 5m
2026-07-08 UAL939 LHR → SFO Jul 8, 15:39 UTCJul 9, 01:40 UTC10h 1m
2026-07-08 UAL930 SFO → LHR Jul 8, 03:39 UTCJul 8, 13:05 UTC9h 26m
2026-07-08 UAL930 SFO → LHR Jul 8, 03:35 UTCJul 8, 13:10 UTC9h 35m
2026-07-07 UAL900 - Jul 7, 10:00 UTCJul 7, 12:40 UTC2h 40m
2026-07-07 UAL900 LHR → SFO Jul 7, 10:00 UTCJul 7, 20:24 UTC10h 24m
2026-07-06 UAL901 SFO → LHR Jul 6, 20:27 UTCJul 7, 05:59 UTC9h 32m
2026-07-06 UAL901 SFO → LHR Jul 6, 20:20 UTCJul 7, 06:05 UTC9h 45m
2026-07-06 UAL2 - Jul 6, 03:55 UTCJul 6, 15:35 UTC11h 40m
2026-07-05 UAL1 - Jul 5, 21:50 UTCJul 5, 22:00 UTC10m
2026-07-05 UAL1 - Jul 5, 06:30 UTCJul 5, 20:40 UTC14h 10m
2026-07-04 UAL939 - Jul 4, 15:45 UTCJul 5, 02:15 UTC10h 30m
2026-07-04 UAL939 LHR → SFO Jul 4, 15:39 UTCJul 5, 02:09 UTC10h 30m
2026-07-04 UAL930 SFO → LHR Jul 4, 03:15 UTCJul 4, 13:05 UTC9h 50m
2026-07-03 UAL900 - Jul 3, 09:50 UTCJul 3, 15:55 UTC6h 5m
2026-07-03 UAL900 LHR → SFO Jul 3, 09:50 UTCJul 3, 20:01 UTC10h 11m
2026-07-02 UAL901 SFO → LHR Jul 2, 20:35 UTCJul 3, 05:50 UTC9h 15m
2026-07-01 UAL939 - Jul 1, 15:45 UTCJul 2, 01:50 UTC10h 5m
2026-07-01 UAL930 SFO → LHR Jul 1, 03:29 UTCJul 1, 12:52 UTC9h 23m

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 N51104 page for operator, model, and routing details .

Mode-S A6679B frequently asked

What is Mode-S code A6679B?
A6679B is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N51104.
Where is Mode-S A6679B registered?
Mode-S code A6679B 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 A6679B broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 16:40 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A6679B, octal 51463633, decimal 10,905,499.
What flights does A6679B operate?
Mode-S A6679B has broadcast 20 distinct callsigns, including UAL1, UAL2, UAL900, UAL901, UAL930.