Apparatus

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sensors Mode-S transponder

A55FA2

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N44501 · AIRBUS A-321neo · operated by UNITED AIRLINES INC

Hex
A55FA2
Octal
51257642
Decimal
10,837,922
Country
US
Tail
N44501
Type
A21N
Broadcasting now · callsign UAL8145 · 11,050 ft
Flights observed
307
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:30 UTC

Current position

A55FA2 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A55FA2 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
UAL2251 United Airlines 6 2026-04-16
UAL1568 United Airlines 6 2026-05-14
UAL2494 United Airlines 5 2026-04-14
UAL1954 - 5 2026-07-11
UAL1253 United Airlines 5 2026-07-23
UAL577 United Airlines 4 2026-07-19
UAL405 United Airlines 4 2026-07-24
UAL360 United Airlines 4 2026-07-24
UAL2113 - 4 2026-07-06
UAL1754 United Airlines 4 2026-04-18
UAL1323 United Airlines 4 2026-05-30
UAL1069 - 4 2026-07-17
UAL8201 United Airlines 3 2026-04-17
UAL789 United Airlines 3 2026-04-24
UAL706 United Airlines 3 2026-05-11
UAL670 - 3 2026-07-10
UAL647 - 3 2026-07-04
UAL618 United Airlines 3 2026-04-24
UAL597 United Airlines 3 2026-05-23
UAL374 United Airlines 3 2026-04-17

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL2061 SAN → EWR Jul 26, 18:30 UTCJul 26, 20:25 UTC1h 55m
2026-07-26 UAL1638 ORD → PHL Jul 26, 14:15 UTCJul 26, 16:10 UTC1h 55m
2026-07-26 UAL377 DEN → ORD Jul 26, 03:35 UTCJul 26, 05:35 UTC2h 0m
2026-07-25 UAL352 IAD → BOS Jul 25, 23:10 UTCJul 26, 01:10 UTC2h 0m
2026-07-25 UAL1311 EWR → CLT Jul 25, 12:30 UTCJul 25, 16:00 UTC3h 30m
2026-07-25 UAL1311 EWR → CLT Jul 25, 12:22 UTCJul 25, 15:59 UTC3h 37m
2026-07-25 UAL1374 DEN → ORF Jul 25, 00:08 UTCJul 25, 03:47 UTC3h 39m
2026-07-25 UAL1374 DEN → ORF Jul 25, 00:10 UTCJul 25, 03:45 UTC3h 35m
2026-07-24 UAL360 DFW → EWR Jul 24, 19:55 UTCJul 24, 22:00 UTC2h 5m
2026-07-24 UAL405 RSW → ORD Jul 24, 16:20 UTCJul 24, 18:15 UTC1h 55m
2026-07-24 UAL2601 RSW → EWR Jul 24, 12:25 UTCJul 24, 14:35 UTC2h 10m
2026-07-24 UAL360 DFW → EWR Jul 24, 02:05 UTCJul 24, 04:30 UTC2h 25m
2026-07-23 UAL1729 DEN → EWR Jul 23, 20:20 UTCJul 24, 00:25 UTC4h 5m
2026-07-23 UAL1442 DEN → LGA Jul 23, 14:30 UTCJul 23, 17:30 UTC3h 0m
2026-07-23 UAL1874 SFO → IND Jul 23, 10:25 UTCJul 23, 12:20 UTC1h 55m
2026-07-23 UAL1253 PHX → ORD Jul 23, 04:05 UTCJul 23, 05:50 UTC1h 45m
2026-07-22 UAL1197 PBI → EWR Jul 22, 22:10 UTCJul 23, 02:01 UTC3h 51m
2026-07-22 UAL1197 PBI → EWR Jul 22, 22:00 UTCJul 23, 02:20 UTC4h 20m
2026-07-22 UAL606 MCO → EWR Jul 22, 17:55 UTCJul 22, 19:25 UTC1h 30m
2026-07-22 UAL1411 SFO → EWR Jul 22, 00:25 UTCJul 22, 02:30 UTC2h 5m
2026-07-21 UAL2803 DEN → SFO Jul 21, 20:05 UTCJul 21, 22:05 UTC2h 0m
2026-07-21 UAL2803 DEN → SFO Jul 21, 20:06 UTCJul 21, 22:02 UTC1h 56m
2026-07-21 UAL2329 DEN → ORD Jul 21, 16:15 UTCJul 21, 18:20 UTC2h 5m
2026-07-21 UAL1889 SFO → IND Jul 21, 12:10 UTCJul 21, 14:15 UTC2h 5m
2026-07-21 UAL1889 SFO → IND Jul 21, 12:12 UTCJul 21, 14:09 UTC1h 57m
2026-07-21 UAL2132 MSP → EWR Jul 21, 02:00 UTCJul 21, 04:10 UTC2h 10m
2026-07-20 UAL1354 SAT → IAD Jul 20, 21:20 UTCJul 20, 23:55 UTC2h 34m
2026-07-20 UAL1354 SAT → IAD Jul 20, 20:35 UTCJul 20, 21:15 UTC40m
2026-07-20 UAL1102 MSN → EWR Jul 20, 16:06 UTCJul 20, 18:31 UTC2h 25m
2026-07-20 UAL1102 MSN → EWR Jul 20, 16:05 UTCJul 20, 18:35 UTC2h 30m
2026-07-20 UAL2631 ORD → MCI Jul 20, 11:40 UTCJul 20, 13:45 UTC2h 5m
2026-07-20 UAL1356 SJC → DEN Jul 20, 00:10 UTCJul 20, 03:35 UTC3h 25m
2026-07-19 UAL577 IAD → DEN Jul 19, 18:55 UTCJul 19, 22:25 UTC3h 30m
2026-07-19 UAL2345 DEN → EWR Jul 19, 12:20 UTCJul 19, 15:30 UTC3h 10m
2026-07-19 UAL1596 PDX → SFO Jul 19, 03:50 UTCJul 19, 05:45 UTC1h 55m
2026-07-18 UAL511 IAH → SFO Jul 18, 22:30 UTCJul 19, 02:20 UTC3h 50m
2026-07-18 UAL2475 MCO → ORD Jul 18, 17:40 UTCJul 18, 20:15 UTC2h 35m
2026-07-18 UAL2475 MCO → ORD Jul 18, 17:34 UTCJul 18, 19:59 UTC2h 25m
2026-07-18 UAL2280 ORD → MCO Jul 18, 13:55 UTCJul 18, 16:05 UTC2h 10m
2026-07-18 UAL1998 ORF → ORD Jul 18, 00:58 UTCJul 18, 02:45 UTC1h 47m
2026-07-18 UAL1998 ORF → ORD Jul 18, 01:05 UTCJul 18, 03:05 UTC2h 1m
2026-07-17 UAL2329 ORD → EWR Jul 17, 20:10 UTCJul 17, 21:44 UTC1h 35m
2026-07-17 UAL1069 - Jul 17, 17:44 UTCJul 17, 18:00 UTC15m
2026-07-17 UAL1069 SAN → ORD Jul 17, 14:02 UTCJul 17, 17:27 UTC3h 25m
2026-07-17 UAL1069 - Jul 17, 14:04 UTCJul 17, 18:00 UTC3h 55m
2026-07-17 UAL1531 - Jul 17, 02:30 UTCJul 17, 05:55 UTC3h 25m
2026-07-16 UAL8130 ORD → ALB Jul 16, 20:35 UTCJul 16, 23:15 UTC2h 40m
2026-07-16 UAL8130 ORD → ALB Jul 16, 20:36 UTCJul 16, 23:01 UTC2h 25m
2026-07-16 UAL2008 ORD → MCO Jul 16, 16:40 UTCJul 16, 18:55 UTC2h 15m
2026-07-16 UAL1775 IAD → ORD Jul 16, 12:30 UTCJul 16, 14:10 UTC1h 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 N44501 page for operator, model, and routing details .

Mode-S A55FA2 frequently asked

What is Mode-S code A55FA2?
A55FA2 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N44501.
Where is Mode-S A55FA2 registered?
Mode-S code A55FA2 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 A55FA2 broadcasting right now?
Yes. Mode-S A55FA2 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A55FA2, octal 51257642, decimal 10,837,922.
What flights does A55FA2 operate?
Mode-S A55FA2 has broadcast 20 distinct callsigns, including UAL2251, UAL1568, UAL2494, UAL1954, UAL1253.