Apparatus

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sensors Mode-S transponder

AA7B4A

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N77471 · operated by UNITED AIRLINES INC

Hex
AA7B4A
Octal
52475512
Decimal
11,172,682
Country
US
Tail
N77471
No current signal · last broadcast Jul 26, 22:30 UTC
Flights observed
4
Distinct callsigns
2
Country
US
Last broadcast
Jul 26, 22:30 UTC

Last known position

Most recent position reported by Mode-S AA7B4A.

Country allocation

The ICAO 24-bit address AA7B4A 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
BOE123 - 3 2026-07-21
BOE971 - 1 2026-07-26

Recent flights last 4

DateFlightRouteTakeoffLandingDuration
2026-07-26 BOE971 - Jul 26, 22:05 UTCJul 26, 22:30 UTC25m
2026-07-21 BOE123 RNT → RNT Jul 21, 03:00 UTCJul 21, 03:05 UTC5m
2026-07-21 BOE123 RNT → RNT Jul 21, 02:15 UTCJul 21, 02:40 UTC25m
2026-07-21 BOE123 RNT → RNT Jul 21, 00:45 UTCJul 21, 01:15 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 N77471 page for operator, model, and routing details .

Mode-S AA7B4A frequently asked

What is Mode-S code AA7B4A?
AA7B4A is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N77471.
Where is Mode-S AA7B4A registered?
Mode-S code AA7B4A 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 AA7B4A broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:30 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AA7B4A, octal 52475512, decimal 11,172,682.
What flights does AA7B4A operate?
Mode-S AA7B4A has broadcast 2 distinct callsigns, including BOE123, BOE971.