sensors Mode-S transponder

AA7E99

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N77542 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
AA7E99
Octal
52477231
Decimal
11,173,529
Country
US
Tail
N77542
Type
B738
No current signal · last broadcast 1d ago
Flights observed
8
Distinct callsigns
5
Country
US
Last broadcast
1d ago

Last known position

Most recent position reported by Mode-S AA7E99.

Country allocation

The ICAO 24-bit address AA7E99 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 5 distinct

Callsign Airline Flights Last seen
UAL2167 - 3 2026-04-13
UAL2350 United Airlines 2 2026-04-13
UAL2322 - 1 2026-04-12
UAL1450 United Airlines 1 2026-04-13
UAL1412 - 1 2026-04-12

Recent flights last 8

DateFlightRouteTakeoffLandingDuration
2026-04-13 UAL1450 EWR → PBI Apr 13, 21:05 UTCApr 13, 23:45 UTC2h 40m
2026-04-13 UAL2167 - Apr 13, 19:45 UTCApr 13, 19:50 UTC5m
2026-04-13 UAL2167 - Apr 13, 16:15 UTCApr 13, 19:50 UTC3h 35m
2026-04-13 UAL2167 - Apr 13, 16:10 UTCApr 13, 19:45 UTC3h 35m
2026-04-13 UAL2350 SAN → ORD Apr 13, 00:20 UTCApr 13, 02:55 UTC2h 35m
2026-04-13 UAL2350 SAN → ORD Apr 13, 00:10 UTCApr 13, 02:55 UTC2h 45m
2026-04-12 UAL1412 - Apr 12, 19:50 UTCApr 12, 20:05 UTC15m
2026-04-12 UAL2322 - Apr 12, 17:40 UTCApr 12, 18:35 UTC55m

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 N77542 page for operator, model, and routing details .

Mode-S AA7E99 frequently asked

What is Mode-S code AA7E99?
AA7E99 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N77542.
Where is Mode-S AA7E99 registered?
Mode-S code AA7E99 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 AA7E99 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 AA7E99, octal 52477231, decimal 11,173,529.
What flights does AA7E99 operate?
Mode-S AA7E99 has broadcast 5 distinct callsigns, including UAL2167, UAL2350, UAL2322, UAL1450, UAL1412.