Apparatus

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sensors Mode-S transponder

A449A4

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N37563 · BOEING 737 MAX 9 · operated by UNITED AIRLINES INC

Hex
A449A4
Octal
51044644
Decimal
10,766,756
Country
US
Tail
N37563
Type
B39M
No current signal · last broadcast Jul 26, 21:40 UTC
Flights observed
359
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:40 UTC

Last known position

Most recent position reported by Mode-S A449A4.

Country allocation

The ICAO 24-bit address A449A4 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
UAL1723 - 8 2026-07-06
UAL693 United Airlines 7 2026-06-11
UAL639 - 5 2026-07-11
UAL533 - 5 2026-04-13
UAL1724 United Airlines 5 2026-07-06
UAL1251 - 5 2026-07-11
UAL1074 - 5 2026-06-12
UAL694 United Airlines 4 2026-06-10
UAL336 United Airlines 4 2026-04-17
UAL2441 United Airlines 4 2026-04-17
UAL1703 United Airlines 4 2026-04-13
UAL1337 United Airlines 4 2026-05-26
UAL1031 United Airlines 4 2026-06-06
UAL778 - 3 2026-07-18
UAL731 - 3 2026-07-05
UAL641 United Airlines 3 2026-06-12
UAL408 - 3 2026-07-14
UAL337 - 3 2026-07-16
UAL2744 United Airlines 3 2026-07-08
UAL2651 United Airlines 3 2026-05-18

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL609 EWR → RDU Jul 26, 19:30 UTCJul 26, 21:35 UTC2h 5m
2026-07-26 UAL356 DEN → TPA Jul 26, 14:10 UTCJul 26, 17:20 UTC3h 10m
2026-07-26 UAL602 BWI → SFO Jul 26, 03:43 UTCJul 26, 06:36 UTC2h 53m
2026-07-26 UAL602 BWI → SFO Jul 26, 03:35 UTCJul 26, 06:40 UTC3h 6m
2026-07-25 UAL1922 IAH → EWR Jul 25, 21:55 UTCJul 25, 23:55 UTC2h 0m
2026-07-25 UAL1922 IAH → EWR Jul 25, 20:11 UTCJul 25, 23:46 UTC3h 35m
2026-07-25 UAL1465 EWR → PLS Jul 25, 15:26 UTCJul 25, 18:50 UTC3h 24m
2026-07-25 UAL1465 EWR → PLS Jul 25, 15:50 UTCJul 25, 17:40 UTC1h 50m
2026-07-25 UAL1905 LGA → DEN Jul 25, 06:30 UTCJul 25, 11:05 UTC4h 35m
2026-07-24 UAL1904 EWR → SFO Jul 24, 23:50 UTCJul 25, 04:10 UTC4h 20m
2026-07-24 UAL2624 LGA → DEN Jul 24, 16:35 UTCJul 24, 19:00 UTC2h 25m
2026-07-24 UAL1115 DEN → MCI Jul 24, 12:40 UTCJul 24, 15:10 UTC2h 30m
2026-07-23 UAL1397 DEN → ORD Jul 23, 20:10 UTCJul 23, 23:15 UTC3h 5m
2026-07-23 UAL392 EWR → MCO Jul 23, 04:35 UTCJul 23, 17:00 UTC12h 25m
2026-07-22 UAL1187 EWR → ATL Jul 22, 23:45 UTCJul 23, 02:20 UTC2h 35m
2026-07-22 UAL1187 EWR → ATL Jul 22, 23:45 UTCJul 23, 02:18 UTC2h 33m
2026-07-22 UAL2659 EGE → ORD Jul 22, 19:45 UTCJul 22, 22:15 UTC2h 30m
2026-07-22 UAL2172 IAH → PHL Jul 22, 15:20 UTCJul 22, 18:00 UTC2h 40m
2026-07-22 UAL2172 IAH → PHL Jul 22, 15:21 UTCJul 22, 17:53 UTC2h 32m
2026-07-21 UAL246 ORD → LGA Jul 21, 19:25 UTCJul 21, 23:35 UTC4h 10m
2026-07-21 UAL1540 - Jul 21, 12:45 UTCJul 21, 17:45 UTC5h 0m
2026-07-20 UAL1907 GUA → IAH Jul 20, 22:15 UTCJul 21, 00:45 UTC2h 29m
2026-07-20 UAL353 SAN → EWR Jul 20, 17:25 UTCJul 20, 20:00 UTC2h 35m
2026-07-20 UAL2018 - Jul 20, 13:40 UTCJul 20, 16:05 UTC2h 25m
2026-07-20 UAL1289 EWR → ATL Jul 20, 10:45 UTCJul 20, 12:10 UTC1h 25m
2026-07-20 UAL3900 - Jul 20, 07:00 UTCJul 20, 08:30 UTC1h 30m
2026-07-20 UAL8203 MEM → ORD Jul 20, 01:50 UTCJul 20, 02:45 UTC55m
2026-07-19 UAL8203 MEM → ORD Jul 19, 23:15 UTCJul 19, 23:30 UTC15m
2026-07-19 UAL1339 - Jul 19, 16:30 UTCJul 19, 21:55 UTC5h 25m
2026-07-18 UAL1534 EWR → FLL Jul 18, 20:55 UTCJul 18, 22:40 UTC1h 45m
2026-07-18 UAL2167 - Jul 18, 17:45 UTCJul 18, 19:35 UTC1h 50m
2026-07-18 UAL1234 GEG → DEN Jul 18, 13:00 UTCJul 18, 14:50 UTC1h 50m
2026-07-18 UAL778 DEN → GEG Jul 18, 02:05 UTCJul 18, 04:00 UTC1h 56m
2026-07-17 UAL8208 - Jul 17, 22:45 UTCJul 18, 00:04 UTC1h 20m
2026-07-17 UAL1311 DEN → DSM Jul 17, 19:40 UTCJul 17, 21:00 UTC1h 20m
2026-07-17 UAL1311 FLL → DEN Jul 17, 19:49 UTCJul 17, 20:57 UTC1h 8m
2026-07-17 UAL640 YVR → DEN Jul 17, 15:49 UTCJul 17, 18:15 UTC2h 25m
2026-07-17 UAL1910 DEN → YVR Jul 17, 03:14 UTCJul 17, 05:50 UTC2h 35m
2026-07-16 UAL2644 PHL → DEN Jul 16, 20:39 UTCJul 16, 23:59 UTC3h 20m
2026-07-16 UAL8110 DEN → PHL Jul 16, 16:15 UTCJul 16, 19:20 UTC3h 5m
2026-07-16 UAL337 PHX → DEN Jul 16, 13:10 UTCJul 16, 14:35 UTC1h 25m
2026-07-16 UAL1236 DEN → PHX Jul 16, 05:45 UTCJul 16, 07:05 UTC1h 20m
2026-07-16 UAL1745 - Jul 16, 02:55 UTCJul 16, 04:25 UTC1h 30m
2026-07-15 UAL2053 ORD → PHX Jul 15, 21:25 UTCJul 16, 00:25 UTC3h 0m
2026-07-15 UAL2443 - Jul 15, 18:15 UTCJul 15, 19:10 UTC55m
2026-07-15 UAL2443 CLE → ORD Jul 15, 18:16 UTCJul 15, 18:50 UTC34m
2026-07-15 UAL2389 PWK → CLE Jul 15, 15:50 UTCJul 15, 16:40 UTC50m
2026-07-15 UAL1733 - Jul 15, 11:30 UTCJul 15, 13:25 UTC1h 55m
2026-07-14 UAL2678 - Jul 14, 17:15 UTCJul 14, 19:00 UTC1h 45m
2026-07-14 UAL408 - Jul 14, 13:00 UTCJul 14, 15:30 UTC2h 30m

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 N37563 page for operator, model, and routing details .

Mode-S A449A4 frequently asked

What is Mode-S code A449A4?
A449A4 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N37563.
Where is Mode-S A449A4 registered?
Mode-S code A449A4 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 A449A4 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:40 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A449A4, octal 51044644, decimal 10,766,756.
What flights does A449A4 operate?
Mode-S A449A4 has broadcast 20 distinct callsigns, including UAL1723, UAL693, UAL639, UAL533, UAL1724.