sensors Mode-S transponder

A65B99

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N509CH · AIRBUS HELICOPTERS EC-145 · operated by CHILDRENS HOSPITAL COLORADO

Hex
A65B99
Octal
51455631
Decimal
10,902,425
Country
US
Tail
N509CH
Type
EC45
No current signal · last broadcast 12h ago
Flights observed
13
Distinct callsigns
1
Country
US
Last broadcast
12h ago

Last known position

Most recent position reported by Mode-S A65B99.

Country allocation

The ICAO 24-bit address A65B99 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 1 distinct

Callsign Airline Flights Last seen
CHILD1 - 13 2026-04-14

Recent flights last 13

DateFlightRouteTakeoffLandingDuration
2026-04-14 CHILD1 - Apr 14, 10:55 UTCApr 14, 11:05 UTC10m
2026-04-14 CHILD1 - Apr 14, 09:30 UTCApr 14, 10:05 UTC35m
2026-04-14 CHILD1 - Apr 14, 08:05 UTCApr 14, 08:10 UTC5m
2026-04-14 CHILD1 - Apr 14, 05:55 UTCApr 14, 06:10 UTC15m
2026-04-13 CHILD1 - Apr 13, 21:55 UTCApr 13, 22:00 UTC5m
2026-04-13 CHILD1 APA → COS Apr 13, 20:20 UTCApr 13, 21:10 UTC50m
2026-04-13 CHILD1 - Apr 13, 19:30 UTCApr 13, 19:40 UTC10m
2026-04-13 CHILD1 - Apr 13, 18:30 UTCApr 13, 18:55 UTC25m
2026-04-13 CHILD1 - Apr 13, 17:25 UTCApr 13, 17:45 UTC20m
2026-04-13 CHILD1 - Apr 13, 05:00 UTCApr 13, 05:35 UTC35m
2026-04-13 CHILD1 - Apr 13, 04:20 UTCApr 13, 04:30 UTC10m
2026-04-13 CHILD1 - Apr 13, 02:20 UTCApr 13, 02:50 UTC30m
2026-04-12 CHILD1 - Apr 12, 18:45 UTCApr 12, 19:25 UTC40m

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 N509CH page for operator, model, and routing details .

Mode-S A65B99 frequently asked

What is Mode-S code A65B99?
A65B99 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N509CH.
Where is Mode-S A65B99 registered?
Mode-S code A65B99 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 A65B99 broadcasting right now?
No active broadcast right now. Last signal was 12h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A65B99, octal 51455631, decimal 10,902,425.
What flights does A65B99 operate?
Mode-S A65B99 has broadcast 1 distinct callsign, including CHILD1.