Apparatus

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sensors Mode-S transponder

A55FE9

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N44522 · operated by UNITED AIRLINES INC

Hex
A55FE9
Octal
51257751
Decimal
10,837,993
Country
US
Tail
N44522
Type
A21N
Broadcasting now · callsign UAL542 · 35,975 ft
Flights observed
425
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:10 UTC

Current position

A55FE9 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address A55FE9 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
UAL1812 - 9 2026-07-07
UAL540 United Airlines 7 2026-06-01
UAL2089 United Airlines 7 2026-07-26
UAL360 - 6 2026-07-02
UAL1596 United Airlines 6 2026-07-16
UAL1561 - 6 2026-07-16
UAL695 United Airlines 5 2026-07-25
UAL2091 - 5 2026-07-11
UAL2033 - 5 2026-07-02
UAL1779 United Airlines 5 2026-06-11
UAL767 - 4 2026-07-07
UAL675 - 4 2026-06-14
UAL647 - 4 2026-07-15
UAL2494 United Airlines 4 2026-06-12
UAL2197 - 4 2026-06-29
UAL1599 - 4 2026-07-15
UAL1568 United Airlines 4 2026-07-20
UAL1525 - 4 2026-07-22
UAL1430 United Airlines 4 2026-05-11
UAL1409 United Airlines 4 2026-05-24

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL2802 IAH → DEN Jul 26, 19:00 UTCJul 26, 21:00 UTC2h 0m
2026-07-26 UAL2089 PDX → SFO Jul 26, 13:30 UTCJul 26, 16:30 UTC3h 0m
2026-07-26 UAL2089 PDX → SFO Jul 26, 11:55 UTCJul 26, 12:05 UTC10m
2026-07-26 UAL2089 PDX → SFO Jul 26, 11:53 UTCJul 26, 16:17 UTC4h 24m
2026-07-25 UAL695 EWR → CLT Jul 25, 20:05 UTCJul 26, 00:10 UTC4h 5m
2026-07-25 UAL2618 IAD → SFO Jul 25, 14:10 UTCJul 25, 17:30 UTC3h 20m
2026-07-24 UAL1801 BUR → SFO Jul 24, 21:45 UTCJul 25, 01:50 UTC4h 5m
2026-07-24 UAL2865 DEN → ORD Jul 24, 17:25 UTCJul 24, 19:30 UTC2h 5m
2026-07-24 UAL1701 PHX → EWR Jul 24, 12:05 UTCJul 24, 15:40 UTC3h 35m
2026-07-24 UAL1745 SFO → IAH Jul 24, 06:15 UTCJul 24, 09:20 UTC3h 5m
2026-07-24 UAL2610 IAD → PDX Jul 24, 02:00 UTCJul 24, 04:10 UTC2h 10m
2026-07-23 UAL374 EWR → PBI Jul 23, 20:25 UTCJul 24, 00:05 UTC3h 40m
2026-07-23 UAL1069 SFO → LAX Jul 23, 14:10 UTCJul 23, 18:05 UTC3h 55m
2026-07-23 UAL1531 ORD → CMH Jul 23, 02:15 UTCJul 23, 05:50 UTC3h 35m
2026-07-22 UAL2497 ORD → BOS Jul 22, 23:05 UTCJul 23, 00:45 UTC1h 40m
2026-07-22 UAL2794 GUM → SFO Jul 22, 19:44 UTCJul 22, 20:57 UTC1h 13m
2026-07-22 UAL2794 GUM → SFO Jul 22, 19:40 UTCJul 22, 20:50 UTC1h 10m
2026-07-22 UAL1525 - Jul 22, 15:40 UTCJul 22, 17:45 UTC2h 5m
2026-07-22 UAL2295 ORD → EWR Jul 22, 11:50 UTCJul 22, 13:20 UTC1h 30m
2026-07-22 UAL2295 ORD → EWR Jul 22, 11:24 UTCJul 22, 13:19 UTC1h 55m
2026-07-21 UAL2320 TPA → EWR Jul 21, 23:30 UTCJul 22, 02:30 UTC3h 0m
2026-07-21 UAL2320 TPA → EWR Jul 21, 23:36 UTCJul 22, 02:16 UTC2h 40m
2026-07-21 UAL777 - Jul 21, 18:05 UTCJul 21, 21:20 UTC3h 15m
2026-07-21 UAL2201 ONT → SFO Jul 21, 15:00 UTCJul 21, 16:45 UTC1h 45m
2026-07-21 UAL1077 EWR → MSP Jul 21, 11:30 UTCJul 21, 12:15 UTC45m
2026-07-21 UAL1077 EWR → MSP Jul 21, 11:24 UTCJul 21, 12:49 UTC1h 25m
2026-07-21 UAL787 SJC → IAH Jul 21, 01:50 UTCJul 21, 04:00 UTC2h 10m
2026-07-20 UAL714 - Jul 20, 21:50 UTCJul 21, 00:05 UTC2h 14m
2026-07-20 UAL714 ORD → IAH Jul 20, 21:38 UTCJul 20, 23:52 UTC2h 14m
2026-07-20 UAL1568 ORD → SFO Jul 20, 15:50 UTCJul 20, 19:50 UTC4h 0m
2026-07-19 UAL511 IAH → SFO Jul 19, 22:00 UTCJul 20, 01:50 UTC3h 50m
2026-07-19 UAL2180 - Jul 19, 18:50 UTCJul 19, 20:15 UTC1h 25m
2026-07-19 UAL8200 - Jul 19, 16:15 UTCJul 19, 17:15 UTC1h 0m
2026-07-18 UAL1777 - Jul 18, 23:45 UTCJul 19, 03:15 UTC3h 30m
2026-07-18 UAL3048 FCO → IAD Jul 18, 17:30 UTCJul 18, 21:10 UTC3h 40m
2026-07-18 UAL1990 AUS → ORD Jul 18, 00:25 UTCJul 18, 02:45 UTC2h 20m
2026-07-17 UAL622 - Jul 17, 19:40 UTCJul 17, 21:44 UTC2h 5m
2026-07-17 UAL2201 DCA → ORD Jul 17, 14:44 UTCJul 17, 16:40 UTC1h 55m
2026-07-17 UAL2201 DCA → ORD Jul 17, 14:43 UTCJul 17, 16:12 UTC1h 29m
2026-07-17 UAL1077 - Jul 17, 11:45 UTCJul 17, 13:15 UTC1h 30m
2026-07-17 UAL353 SAN → EWR Jul 17, 05:55 UTCJul 17, 09:35 UTC3h 40m
2026-07-17 UAL1262 DEN → LAX Jul 17, 02:03 UTCJul 17, 03:52 UTC1h 49m
2026-07-17 UAL1262 DEN → LAX Jul 17, 02:05 UTCJul 17, 04:04 UTC2h 0m
2026-07-16 UAL1596 PDX → SFO Jul 16, 22:00 UTCJul 16, 23:59 UTC2h 0m
2026-07-16 UAL1561 DEN → SFO Jul 16, 18:05 UTCJul 16, 20:15 UTC2h 10m
2026-07-15 UAL484 - Jul 15, 22:10 UTCJul 16, 00:10 UTC2h 0m
2026-07-15 UAL1599 - Jul 15, 18:05 UTCJul 15, 20:25 UTC2h 20m
2026-07-15 UAL647 BOS → DEN Jul 15, 11:55 UTCJul 15, 15:45 UTC3h 50m
2026-07-14 UAL597 DEN → BOS Jul 14, 20:24 UTCJul 14, 23:56 UTC3h 32m
2026-07-14 UAL597 DEN → BOS Jul 14, 20:20 UTCJul 15, 00:00 UTC3h 39m

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 N44522 page for operator, model, and routing details .

Mode-S A55FE9 frequently asked

What is Mode-S code A55FE9?
A55FE9 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N44522.
Where is Mode-S A55FE9 registered?
Mode-S code A55FE9 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 A55FE9 broadcasting right now?
Yes. Mode-S A55FE9 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A55FE9, octal 51257751, decimal 10,837,993.
What flights does A55FE9 operate?
Mode-S A55FE9 has broadcast 20 distinct callsigns, including UAL1812, UAL540, UAL2089, UAL360, UAL1596.