Apparatus

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sensors Mode-S transponder

A666CD

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N511SY · EMBRAER ERJ-170-200 (long wing) · operated by SKYWEST AIRLINES INC

Hex
A666CD
Octal
51463315
Decimal
10,905,293
Country
US
Tail
N511SY
Type
E75L
No current signal · last broadcast Jul 26, 18:30 UTC
Flights observed
642
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 18:30 UTC

Last known position

Most recent position reported by Mode-S A666CD.

Country allocation

The ICAO 24-bit address A666CD 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
SKW6381 - 23 2026-07-16
SKW4987 SkyWest Airlines 21 2026-05-18
SKW6185 - 18 2026-07-15
SKW6307 SkyWest Airlines 16 2026-07-20
SKW6278 - 16 2026-07-17
SKW6346 SkyWest Airlines 15 2026-07-21
SKW4958 - 15 2026-07-14
SKW4913 SkyWest Airlines 15 2026-05-21
SKW6393 SkyWest Airlines 14 2026-07-22
SKW6190 - 14 2026-07-19
SKW6272 - 13 2026-07-14
SKW5000 - 12 2026-07-18
SKW4979 - 12 2026-07-14
SKW4977 SkyWest Airlines 12 2026-06-20
SKW6409 - 10 2026-06-30
SKW6293 - 10 2026-07-18
SKW6270 SkyWest Airlines 10 2026-07-21
SKW4957 - 10 2026-06-19
SKW6425 SkyWest Airlines 9 2026-07-22
SKW6330 - 9 2026-07-03

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 SKW4983 CID → PHX Jul 26, 15:45 UTCJul 26, 18:25 UTC2h 40m
2026-07-26 SKW260X SAV → ORD Jul 26, 14:25 UTCJul 26, 15:00 UTC35m
2026-07-26 SKW4982 STL → DFW Jul 26, 02:55 UTCJul 26, 06:25 UTC3h 30m
2026-07-26 SKW6220 BFL → PHX Jul 26, 01:45 UTCJul 26, 02:00 UTC15m
2026-07-25 SKW6220 BFL → PHX Jul 25, 23:15 UTCJul 26, 02:00 UTC2h 45m
2026-07-25 SKW6220 BFL → PHX Jul 25, 23:12 UTCJul 26, 01:28 UTC2h 16m
2026-07-25 SKW6220 BFL → PHX Jul 25, 19:10 UTCJul 25, 20:15 UTC1h 5m
2026-07-25 SKW4970 ORD → RST Jul 25, 16:50 UTCJul 25, 17:40 UTC50m
2026-07-25 SKW4970 ORD → RST Jul 25, 15:00 UTCJul 25, 15:45 UTC45m
2026-07-25 SKW4893 YUM → PHX Jul 25, 11:20 UTCJul 25, 13:35 UTC2h 15m
2026-07-25 SKW6420 SEA → LAX Jul 25, 02:25 UTCJul 25, 04:45 UTC2h 20m
2026-07-25 SKW6368 PHX → ELP Jul 25, 00:40 UTCJul 25, 01:00 UTC20m
2026-07-24 SKW6368 PHX → ELP Jul 24, 23:20 UTCJul 24, 23:45 UTC25m
2026-07-24 SKW4925 PHX → HMO Jul 24, 19:55 UTCJul 24, 20:50 UTC55m
2026-07-24 SKW4925 PHX → HMO Jul 24, 19:54 UTCJul 24, 20:45 UTC51m
2026-07-24 SKW4925 PHX → HMO Jul 24, 18:15 UTCJul 24, 19:05 UTC50m
2026-07-24 SKW6475 PHX → DRO Jul 24, 14:20 UTCJul 24, 16:15 UTC1h 55m
2026-07-24 SKW6475 PHX → DRO Jul 24, 14:18 UTCJul 24, 16:09 UTC1h 51m
2026-07-24 SKW6332 LAX → AUS Jul 24, 02:40 UTCJul 24, 04:25 UTC1h 45m
2026-07-23 SKW4934 PHX → MFR Jul 23, 23:30 UTCJul 24, 01:25 UTC1h 55m
2026-07-23 SKW4934 PHX → MFR Jul 23, 21:00 UTCJul 23, 22:40 UTC1h 40m
2026-07-23 SKW4995 DFW → LAW Jul 23, 18:25 UTCJul 23, 19:35 UTC1h 10m
2026-07-23 SKW4995 DFW → LAW Jul 23, 16:10 UTCJul 23, 17:15 UTC1h 5m
2026-07-23 SKW6404 SFO → PHX Jul 23, 13:25 UTCJul 23, 15:00 UTC1h 35m
2026-07-23 SKW6260 LAX → SFO Jul 23, 04:45 UTCJul 23, 05:45 UTC1h 0m
2026-07-22 SKW4971 DFW → LRD Jul 22, 23:55 UTCJul 23, 03:10 UTC3h 15m
2026-07-22 SKW4971 DFW → LRD Jul 22, 19:45 UTCJul 22, 22:40 UTC2h 55m
2026-07-22 SKW6425 MAF → DFW Jul 22, 17:25 UTCJul 22, 18:05 UTC40m
2026-07-22 SKW6425 MAF → DFW Jul 22, 15:35 UTCJul 22, 16:25 UTC50m
2026-07-22 SKW6393 TUS → LAX Jul 22, 13:05 UTCJul 22, 14:15 UTC1h 10m
2026-07-22 SKW6393 TUS → LAX Jul 22, 13:03 UTCJul 22, 14:11 UTC1h 8m
2026-07-22 SKW6315 LAX → ABQ Jul 22, 02:30 UTCJul 22, 03:35 UTC1h 5m
2026-07-21 SKW6270 LAX → SFO Jul 21, 23:15 UTCJul 22, 01:35 UTC2h 20m
2026-07-21 SKW6270 LAX → SFO Jul 21, 19:45 UTCJul 21, 21:35 UTC1h 50m
2026-07-21 SKW6336 PHX → ICT Jul 21, 16:25 UTCJul 21, 17:25 UTC1h 0m
2026-07-21 SKW6336 PHX → ICT Jul 21, 16:24 UTCJul 21, 17:27 UTC1h 3m
2026-07-21 SKW6336 PHX → ICT Jul 21, 14:25 UTCJul 21, 15:20 UTC55m
2026-07-21 SKW6346 ORD → BNA Jul 21, 02:30 UTCJul 21, 03:45 UTC1h 15m
2026-07-21 SKW6346 ORD → BNA Jul 21, 00:35 UTCJul 21, 01:35 UTC1h 0m
2026-07-20 SKW6307 DFW → SHV Jul 20, 20:30 UTCJul 20, 23:10 UTC2h 40m
2026-07-20 SKW6307 DFW → SHV Jul 20, 16:50 UTCJul 20, 19:25 UTC2h 35m
2026-07-20 SKW4919 SBA → PHX Jul 20, 13:10 UTCJul 20, 14:45 UTC1h 35m
2026-07-20 SKW296Y - Jul 20, 03:20 UTCJul 20, 04:55 UTC1h 35m
2026-07-20 SKW4946 - Jul 20, 01:25 UTCJul 20, 02:05 UTC40m
2026-07-19 SKW6190 - Jul 19, 23:25 UTCJul 20, 00:15 UTC50m
2026-07-19 SKW6188 - Jul 19, 21:20 UTCJul 19, 22:20 UTC1h 0m
2026-07-19 SKW6188 SFO → LAX Jul 19, 21:17 UTCJul 19, 22:17 UTC1h 0m
2026-07-19 SKW6188 - Jul 19, 19:20 UTCJul 19, 20:20 UTC1h 0m
2026-07-19 SKW6336 PHX → ICT Jul 19, 17:15 UTCJul 19, 18:15 UTC1h 0m
2026-07-19 SKW6336 PHX → ICT Jul 19, 15:20 UTCJul 19, 16:20 UTC1h 0m

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 N511SY page for operator, model, and routing details .

Mode-S A666CD frequently asked

What is Mode-S code A666CD?
A666CD is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N511SY.
Where is Mode-S A666CD registered?
Mode-S code A666CD 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 A666CD broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 18:30 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A666CD, octal 51463315, decimal 10,905,293.
What flights does A666CD operate?
Mode-S A666CD has broadcast 20 distinct callsigns, including SKW6381, SKW4987, SKW6185, SKW6307, SKW6278.