Apparatus

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sensors Mode-S transponder

A1C05D

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N21154 · EMBRAER ERJ-145XR · operated by UNITED AIRLINES INC

Hex
A1C05D
Octal
50340135
Decimal
10,600,541
Country
US
Tail
N21154
Type
E45X
Transponder active on ground
Flights observed
641
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 19:20 UTC

Last known position

Most recent position reported by Mode-S A1C05D.

Country allocation

The ICAO 24-bit address A1C05D 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
UCA4288 - 9 2026-07-02
UCA4229 - 9 2026-07-02
UCA4349 CommutAir 8 2026-07-23
UCA4896 - 7 2026-07-15
UCA4835 - 7 2026-07-14
UCA4356 CommutAir 7 2026-06-15
UCA4331 CommutAir 7 2026-07-11
UCA4282 CommutAir 7 2026-06-06
UCA4266 - 7 2026-07-10
UCA4929 - 6 2026-07-05
UCA4906 CommutAir 6 2026-06-15
UCA4837 - 6 2026-07-08
UCA4832 - 6 2026-07-15
UCA4818 CommutAir 6 2026-07-24
UCA4813 CommutAir 6 2026-06-08
UCA4365 - 6 2026-07-05
UCA4361 - 6 2026-07-16
UCA4355 - 6 2026-07-14
UCA4347 CommutAir 6 2026-05-20
UCA4344 - 6 2026-07-16

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UCA4328 IAD → CMH Jul 26, 18:55 UTCJul 26, 19:20 UTC25m
2026-07-26 UCA4815 IAD → CHO Jul 26, 17:05 UTCJul 26, 17:40 UTC35m
2026-07-25 UCA4926 IAD → ALB Jul 25, 22:50 UTCJul 25, 23:45 UTC55m
2026-07-25 UCA4237 IAH → MFE Jul 25, 19:15 UTCJul 25, 20:40 UTC1h 25m
2026-07-25 UCA4333 IAD → BDL Jul 25, 17:00 UTCJul 25, 18:15 UTC1h 15m
2026-07-25 UCA4857 - Jul 25, 13:50 UTCJul 25, 15:10 UTC1h 20m
2026-07-25 UCA4270 MFE → IAH Jul 25, 02:10 UTCJul 25, 03:30 UTC1h 20m
2026-07-25 UCA4270 MFE → IAH Jul 25, 00:00 UTCJul 25, 00:55 UTC55m
2026-07-24 UCA4823 PVD → IAD Jul 24, 22:05 UTCJul 24, 22:50 UTC45m
2026-07-24 UCA4268 MDT → IAD Jul 24, 19:10 UTCJul 24, 19:35 UTC25m
2026-07-24 UCA4372 IAD → MDT Jul 24, 16:55 UTCJul 24, 17:20 UTC25m
2026-07-24 UCA4283 IAD → CMH Jul 24, 14:45 UTCJul 24, 15:45 UTC1h 0m
2026-07-24 UCA4818 ORF → IAD Jul 24, 12:25 UTCJul 24, 13:35 UTC1h 10m
2026-07-24 UCA4251 IAD → BUF Jul 24, 10:35 UTCJul 24, 11:20 UTC45m
2026-07-24 UCA4849 OKC → IAH Jul 24, 02:15 UTCJul 24, 03:15 UTC1h 0m
2026-07-24 UCA4322 IAD → PVD Jul 24, 00:15 UTCJul 24, 01:25 UTC1h 10m
2026-07-23 UCA4310 IAD → BTV Jul 23, 21:20 UTCJul 23, 23:00 UTC1h 40m
2026-07-23 UCA4327 IAD → SYR Jul 23, 19:15 UTCJul 23, 20:00 UTC45m
2026-07-23 UCA4327 IAD → SYR Jul 23, 19:23 UTCJul 23, 19:49 UTC26m
2026-07-23 UCA4349 IAD → BTV Jul 23, 17:35 UTCJul 23, 18:20 UTC45m
2026-07-23 UCA4324 - Jul 23, 15:20 UTCJul 23, 16:15 UTC55m
2026-07-23 UCA4324 MYR → IAD Jul 23, 15:11 UTCJul 23, 16:27 UTC1h 16m
2026-07-23 UCA4336 IAD → PVD Jul 23, 12:25 UTCJul 23, 13:50 UTC1h 25m
2026-07-23 UCA4860 - Jul 23, 10:10 UTCJul 23, 11:10 UTC1h 0m
2026-07-23 UCA4860 SYR → IAD Jul 23, 10:25 UTCJul 23, 11:07 UTC42m
2026-07-23 UCA4856 IAH → CRP Jul 23, 02:35 UTCJul 23, 03:40 UTC1h 5m
2026-07-23 UCA4861 IAH → LIT Jul 23, 00:00 UTCJul 23, 01:15 UTC1h 15m
2026-07-22 UCA4871 IAD → ROC Jul 22, 22:00 UTCJul 22, 22:50 UTC50m
2026-07-22 UCA4871 IAD → ROC Jul 22, 21:53 UTCJul 22, 23:00 UTC1h 7m
2026-07-22 UCA4925 - Jul 22, 19:10 UTCJul 22, 20:40 UTC1h 30m
2026-07-22 UCA4930 IAD → MHT Jul 22, 16:25 UTCJul 22, 17:45 UTC1h 20m
2026-07-22 UCA4325 - Jul 22, 14:20 UTCJul 22, 15:30 UTC1h 10m
2026-07-21 UCA4914 IAD → TYS Jul 21, 23:20 UTCJul 22, 00:30 UTC1h 10m
2026-07-21 UCA4349 IAD → BTV Jul 21, 17:20 UTCJul 21, 17:40 UTC20m
2026-07-21 UCA4834 - Jul 21, 15:00 UTCJul 21, 15:25 UTC25m
2026-07-21 UCA4319 IAD → SCE Jul 21, 13:01 UTCJul 21, 13:34 UTC33m
2026-07-21 UCA4319 - Jul 21, 12:45 UTCJul 21, 13:30 UTC45m
2026-07-21 UCA4970 ALB → IAD Jul 21, 10:20 UTCJul 21, 11:30 UTC1h 10m
2026-07-21 UCA4970 ALB → IAD Jul 21, 10:26 UTCJul 21, 11:24 UTC58m
2026-07-20 UCA4926 IAD → ALB Jul 20, 21:45 UTCJul 20, 22:55 UTC1h 10m
2026-07-20 UCA4926 IAD → ALB Jul 20, 21:53 UTCJul 20, 22:49 UTC56m
2026-07-20 UCA4938 - Jul 20, 18:55 UTCJul 20, 19:25 UTC30m
2026-07-20 UCA4253 - Jul 20, 17:30 UTCJul 20, 17:50 UTC20m
2026-07-20 UCA4253 IAD → SCE Jul 20, 17:15 UTCJul 20, 17:57 UTC42m
2026-07-20 UCA4324 - Jul 20, 14:50 UTCJul 20, 15:40 UTC50m
2026-07-20 UCA4236 - Jul 20, 12:35 UTCJul 20, 13:35 UTC1h 0m
2026-07-20 UCA4861 ROC → IAD Jul 20, 00:10 UTCJul 20, 01:00 UTC50m
2026-07-19 UCA4871 IAD → ROC Jul 19, 22:00 UTCJul 19, 22:45 UTC45m
2026-07-19 UCA4848 TYS → IAD Jul 19, 17:45 UTCJul 19, 19:00 UTC1h 15m
2026-07-19 UCA4833 - Jul 19, 13:25 UTCJul 19, 15:10 UTC1h 45m

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 N21154 page for operator, model, and routing details .

Mode-S A1C05D frequently asked

What is Mode-S code A1C05D?
A1C05D is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N21154.
Where is Mode-S A1C05D registered?
Mode-S code A1C05D 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 A1C05D broadcasting right now?
Mode-S A1C05D is currently broadcasting from the ground.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1C05D, octal 50340135, decimal 10,600,541.
What flights does A1C05D operate?
Mode-S A1C05D has broadcast 20 distinct callsigns, including UCA4288, UCA4229, UCA4349, UCA4896, UCA4835.