sensors Mode-S transponder

A747CB

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N56859 · BOEING 757-300 · operated by UNITED AIRLINES INC

Hex
A747CB
Octal
51643713
Decimal
10,962,891
Country
US
Tail
N56859
Type
B753
No current signal · last broadcast 1d ago
Flights observed
6
Distinct callsigns
2
Country
US
Last broadcast
1d ago

Last known position

Most recent position reported by Mode-S A747CB.

Country allocation

The ICAO 24-bit address A747CB 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 2 distinct

Callsign Airline Flights Last seen
UAL4204 - 4 2026-04-13
UAL4203 - 2 2026-04-12

Recent flights last 6

DateFlightRouteTakeoffLandingDuration
2026-04-13 UAL4204 - Apr 13, 19:50 UTCApr 13, 20:35 UTC45m
2026-04-13 UAL4204 - Apr 13, 18:30 UTCApr 13, 20:10 UTC1h 40m
2026-04-13 UAL4204 - Apr 13, 13:12 UTCApr 13, 20:01 UTC6h 49m
2026-04-13 UAL4204 - Apr 13, 13:42 UTCApr 13, 20:33 UTC6h 51m
2026-04-12 UAL4203 - Apr 12, 16:12 UTCApr 12, 23:05 UTC6h 53m
2026-04-12 UAL4203 - Apr 12, 17:15 UTCApr 12, 17:45 UTC30m

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 N56859 page for operator, model, and routing details .

Mode-S A747CB frequently asked

What is Mode-S code A747CB?
A747CB is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N56859.
Where is Mode-S A747CB registered?
Mode-S code A747CB 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 A747CB broadcasting right now?
No active broadcast right now. Last signal was 1d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A747CB, octal 51643713, decimal 10,962,891.
What flights does A747CB operate?
Mode-S A747CB has broadcast 2 distinct callsigns, including UAL4204, UAL4203.