Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

AA4C1A

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N76254 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
AA4C1A
Octal
52446032
Decimal
11,160,602
Country
US
Tail
N76254
Type
B738
No current signal · last broadcast Jul 26, 22:15 UTC
Flights observed
435
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:15 UTC

Last known position

Most recent position reported by Mode-S AA4C1A.

Country allocation

The ICAO 24-bit address AA4C1A 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
UAL1405 - 6 2026-07-12
UAL1911 - 5 2026-06-30
UAL1408 - 5 2026-07-12
UAL590 - 4 2026-07-01
UAL275 - 4 2026-06-30
UAL2201 United Airlines 4 2026-06-12
UAL1919 - 4 2026-07-08
UAL1867 - 4 2026-07-08
UAL1592 United Airlines 4 2026-05-18
UAL1303 United Airlines 4 2026-07-22
UAL717 United Airlines 3 2026-07-26
UAL703 United Airlines 3 2026-06-01
UAL669 United Airlines 3 2026-04-29
UAL654K United Airlines 3 2026-06-08
UAL493 United Airlines 3 2026-07-24
UAL390 - 3 2026-07-11
UAL2684 United Airlines 3 2026-05-17
UAL2457 United Airlines 3 2026-04-26
UAL2043 United Airlines 3 2026-04-26
UAL1902 United Airlines 3 2026-05-03

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL717 MFR → SFO Jul 26, 18:10 UTCJul 26, 22:15 UTC4h 5m
2026-07-26 UAL1604 SFO → BNA Jul 26, 15:45 UTCJul 26, 16:40 UTC55m
2026-07-26 UAL589 DEN → RIC Jul 26, 02:35 UTCJul 26, 03:40 UTC1h 5m
2026-07-26 UAL2841 DEN → IAH Jul 26, 00:05 UTCJul 26, 01:15 UTC1h 10m
2026-07-25 UAL2855 EWR → SFO Jul 25, 21:20 UTCJul 25, 22:30 UTC1h 10m
2026-07-25 UAL1712 LAX → SFO Jul 25, 16:50 UTCJul 25, 19:55 UTC3h 5m
2026-07-25 UAL1712 LAX → SFO Jul 25, 16:34 UTCJul 25, 19:51 UTC3h 17m
2026-07-25 UAL539 PHL → SFO Jul 25, 12:55 UTCJul 25, 14:35 UTC1h 40m
2026-07-25 UAL2768 IAH → SFO Jul 25, 00:40 UTCJul 25, 02:45 UTC2h 5m
2026-07-24 UAL2809 ORF → ORD Jul 24, 21:25 UTCJul 24, 23:05 UTC1h 40m
2026-07-24 UAL493 CLE → IAD Jul 24, 19:50 UTCJul 24, 19:55 UTC5m
2026-07-24 UAL493 CLE → IAD Jul 24, 19:00 UTCJul 24, 19:55 UTC55m
2026-07-24 UAL493 CLE → IAD Jul 24, 18:46 UTCJul 24, 19:35 UTC49m
2026-07-24 UAL2849 EWR → DOM Jul 24, 16:35 UTCJul 24, 17:15 UTC40m
2026-07-24 UAL1811 ORD → BDL Jul 24, 12:25 UTCJul 24, 14:15 UTC1h 50m
2026-07-24 UAL1510 IAD → PHX Jul 24, 02:25 UTCJul 24, 05:15 UTC2h 50m
2026-07-23 UAL1389 CMH → DEN Jul 23, 20:35 UTCJul 23, 23:25 UTC2h 50m
2026-07-23 UAL480 DFW → EWR Jul 23, 16:55 UTCJul 23, 19:15 UTC2h 20m
2026-07-23 UAL2865 DEN → ORD Jul 23, 12:15 UTCJul 23, 14:15 UTC2h 0m
2026-07-23 UAL2479 ORD → LAS Jul 23, 03:00 UTCJul 23, 05:00 UTC2h 0m
2026-07-22 UAL1303 EWR → IAH Jul 22, 23:20 UTCJul 23, 01:25 UTC2h 5m
2026-07-22 UAL1303 EWR → IAH Jul 22, 23:04 UTCJul 23, 01:21 UTC2h 17m
2026-07-22 UAL2290 ORD → SFO Jul 22, 18:40 UTCJul 22, 20:25 UTC1h 45m
2026-07-22 UAL1310 EWR → JAX Jul 22, 14:38 UTCJul 22, 17:01 UTC2h 23m
2026-07-22 UAL1310 EWR → JAX Jul 22, 15:05 UTCJul 22, 17:10 UTC2h 5m
2026-07-22 UAL2617 SFO → LAX Jul 22, 11:35 UTCJul 22, 13:10 UTC1h 35m
2026-07-22 UAL2124 PDX → SFO Jul 22, 04:50 UTCJul 22, 05:25 UTC35m
2026-07-21 UAL1310 EWR → JAX Jul 21, 15:50 UTCJul 21, 17:55 UTC2h 5m
2026-07-21 UAL2617 SFO → LAX Jul 21, 11:25 UTCJul 21, 13:30 UTC2h 5m
2026-07-21 UAL2094 IAH → LGA Jul 21, 05:50 UTCJul 21, 09:00 UTC3h 10m
2026-07-21 UAL2262 LAS → SFO Jul 21, 03:05 UTCJul 21, 04:15 UTC1h 10m
2026-07-21 UAL2019 OGG → SFO Jul 21, 00:10 UTCJul 21, 01:10 UTC1h 0m
2026-07-20 UAL547 IAH → SFO Jul 20, 16:15 UTCJul 20, 21:45 UTC5h 30m
2026-07-20 UAL1006 LAX → SFO Jul 20, 13:40 UTCJul 20, 14:05 UTC25m
2026-07-20 UAL1863 PUJ → ORD Jul 20, 04:50 UTCJul 20, 06:00 UTC1h 10m
2026-07-19 UAL1881 - Jul 19, 19:15 UTCJul 20, 01:40 UTC6h 25m
2026-07-19 UAL1372 - Jul 19, 16:40 UTCJul 19, 17:30 UTC50m
2026-07-19 UAL2655 - Jul 19, 14:15 UTCJul 19, 15:05 UTC50m
2026-07-19 UAL1363 SJC → DEN Jul 19, 01:55 UTCJul 19, 02:30 UTC35m
2026-07-19 UAL1363 SJC → DEN Jul 19, 02:05 UTCJul 19, 02:40 UTC35m
2026-07-18 UAL797 DEN → ICT Jul 18, 18:50 UTCJul 19, 00:00 UTC5h 10m
2026-07-18 UAL354 ORD → BTV Jul 18, 11:30 UTCJul 18, 15:30 UTC4h 0m
2026-07-17 UAL1692 - Jul 17, 18:05 UTCJul 17, 22:15 UTC4h 10m
2026-07-17 UAL2318 - Jul 17, 11:10 UTCJul 17, 15:55 UTC4h 45m
2026-07-17 UAL675 ORD → BWI Jul 17, 03:20 UTCJul 17, 04:44 UTC1h 25m
2026-07-16 UAL791 BZN → ORD Jul 16, 22:55 UTCJul 17, 00:40 UTC1h 45m
2026-07-16 UAL2124 ORD → BWI Jul 16, 20:00 UTCJul 16, 21:19 UTC1h 20m
2026-07-16 UAL2306 - Jul 16, 14:10 UTCJul 16, 17:40 UTC3h 30m
2026-07-16 UAL2306 PDX → ORD Jul 16, 14:12 UTCJul 16, 17:25 UTC3h 13m
2026-07-15 UAL1677 - Jul 15, 21:40 UTCJul 16, 01:20 UTC3h 40m

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 N76254 page for operator, model, and routing details .

Mode-S AA4C1A frequently asked

What is Mode-S code AA4C1A?
AA4C1A is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N76254.
Where is Mode-S AA4C1A registered?
Mode-S code AA4C1A 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 AA4C1A broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AA4C1A, octal 52446032, decimal 11,160,602.
What flights does AA4C1A operate?
Mode-S AA4C1A has broadcast 20 distinct callsigns, including UAL1405, UAL1911, UAL1408, UAL590, UAL275.