Apparatus

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sensors Mode-S transponder

A44981

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N37553 · BOEING 737 MAX 9 · operated by UNITED AIRLINES INC

Hex
A44981
Octal
51044601
Decimal
10,766,721
Country
US
Tail
N37553
Type
B39M
No current signal · last broadcast Jul 26, 22:15 UTC
Flights observed
456
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:15 UTC

Last known position

Most recent position reported by Mode-S A44981.

Country allocation

The ICAO 24-bit address A44981 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
UAL1176 United Airlines 8 2026-05-20
UAL638 United Airlines 6 2026-05-20
UAL446 - 5 2026-04-17
UAL699 United Airlines 4 2026-07-19
UAL569 - 4 2026-07-14
UAL308 United Airlines 4 2026-04-14
UAL1988 - 4 2026-07-13
UAL1724 United Airlines 4 2026-06-20
UAL1723 - 4 2026-06-20
UAL1703 - 4 2026-07-14
UAL1631 United Airlines 4 2026-04-16
UAL1618 - 4 2026-07-05
UAL1575 United Airlines 4 2026-04-14
UAL1465 - 4 2026-07-14
UAL1461 - 4 2026-07-08
UAL1367 - 4 2026-06-23
UAL1171 - 4 2026-07-17
UAL1144 - 4 2026-07-16
UAL1040 - 4 2026-07-17
UAL1036 - 4 2026-07-21

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1270 ORD → PUJ Jul 26, 14:15 UTCJul 26, 22:15 UTC8h 0m
2026-07-25 UAL1121 IAH → MSY Jul 25, 13:20 UTCJul 25, 23:55 UTC10h 35m
2026-07-25 UAL1210 EWR → ATL Jul 25, 01:00 UTCJul 25, 04:20 UTC3h 20m
2026-07-24 UAL1254 PSP → SFO Jul 24, 22:00 UTCJul 24, 23:30 UTC1h 30m
2026-07-24 UAL1715 DEN → EWR Jul 24, 18:05 UTCJul 24, 20:00 UTC1h 55m
2026-07-24 UAL1826 SFO → DEN Jul 24, 10:50 UTCJul 24, 16:05 UTC5h 15m
2026-07-23 UAL286 CLE → DEN Jul 23, 21:45 UTCJul 24, 01:10 UTC3h 25m
2026-07-23 UAL1155 DEN → IND Jul 23, 16:45 UTCJul 23, 20:05 UTC3h 20m
2026-07-22 UAL1471 EWR → SDQ Jul 22, 23:35 UTCJul 23, 13:45 UTC14h 10m
2026-07-22 UAL1892 - Jul 22, 19:35 UTCJul 22, 20:40 UTC1h 5m
2026-07-22 UAL486 MCO → CLE Jul 22, 15:50 UTCJul 22, 17:50 UTC2h 0m
2026-07-22 UAL2636 - Jul 22, 12:20 UTCJul 22, 14:20 UTC2h 0m
2026-07-21 UAL744 - Jul 21, 23:25 UTCJul 22, 01:50 UTC2h 25m
2026-07-21 UAL1036 - Jul 21, 17:55 UTCJul 21, 20:05 UTC2h 10m
2026-07-21 UAL2009 IAH → LIR Jul 21, 12:25 UTCJul 21, 14:40 UTC2h 15m
2026-07-21 UAL2009 IAH → LIR Jul 21, 12:24 UTCJul 21, 15:25 UTC3h 1m
2026-07-21 UAL2495 - Jul 21, 08:00 UTCJul 21, 10:20 UTC2h 20m
2026-07-21 UAL2495 - Jul 21, 06:15 UTCJul 21, 06:30 UTC15m
2026-07-21 UAL2025 - Jul 21, 01:10 UTCJul 21, 01:30 UTC20m
2026-07-20 UAL2025 - Jul 20, 22:05 UTCJul 20, 23:05 UTC1h 0m
2026-07-20 UAL1694 CUN → IAD Jul 20, 16:30 UTCJul 20, 19:45 UTC3h 15m
2026-07-20 UAL1619 - Jul 20, 13:00 UTCJul 20, 14:50 UTC1h 50m
2026-07-20 UAL1619 IAH → IAH Jul 20, 12:45 UTCJul 20, 12:50 UTC5m
2026-07-20 UAL1475 EWR → RSW Jul 20, 00:05 UTCJul 20, 02:05 UTC2h 0m
2026-07-19 UAL699 BWI → SFO Jul 19, 19:50 UTCJul 19, 22:00 UTC2h 10m
2026-07-19 UAL699 BWI → SFO Jul 19, 19:50 UTCJul 19, 21:42 UTC1h 52m
2026-07-19 UAL1181 MIA → EWR Jul 19, 15:10 UTCJul 19, 17:50 UTC2h 40m
2026-07-19 UAL2406 LAX → SFO Jul 19, 00:10 UTCJul 19, 02:50 UTC2h 40m
2026-07-18 UAL1468 - Jul 18, 20:05 UTCJul 18, 22:35 UTC2h 30m
2026-07-18 UAL1441 IAH → SAL Jul 18, 15:40 UTCJul 18, 18:00 UTC2h 20m
2026-07-18 UAL537 - Jul 18, 12:55 UTCJul 18, 14:00 UTC1h 5m
2026-07-18 UAL1794 - Jul 18, 01:45 UTCJul 18, 02:45 UTC1h 0m
2026-07-17 UAL1171 - Jul 17, 19:20 UTCJul 17, 23:20 UTC4h 0m
2026-07-17 UAL1171 AUA → IAH Jul 17, 19:24 UTCJul 17, 23:17 UTC3h 53m
2026-07-17 UAL1040 - Jul 17, 17:25 UTCJul 17, 17:40 UTC15m
2026-07-17 UAL1040 - Jul 17, 13:45 UTCJul 17, 14:30 UTC45m
2026-07-16 UAL1047 CUN → EWR Jul 16, 23:25 UTCJul 17, 02:34 UTC3h 10m
2026-07-16 UAL1047 CUN → EWR Jul 16, 23:30 UTCJul 17, 02:31 UTC3h 1m
2026-07-16 UAL1987 - Jul 16, 18:00 UTCJul 16, 21:15 UTC3h 15m
2026-07-16 UAL1144 - Jul 16, 13:49 UTCJul 16, 15:49 UTC2h 0m
2026-07-16 UAL1144 JAX → EWR Jul 16, 13:46 UTCJul 16, 15:45 UTC1h 59m
2026-07-16 UAL1207 - Jul 16, 10:20 UTCJul 16, 12:14 UTC1h 55m
2026-07-16 UAL499 BNA → EWR Jul 16, 03:20 UTCJul 16, 05:10 UTC1h 50m
2026-07-16 UAL499 BNA → EWR Jul 16, 03:17 UTCJul 16, 05:05 UTC1h 48m
2026-07-15 UAL2454 EWR → BNA Jul 15, 20:15 UTCJul 15, 21:55 UTC1h 40m
2026-07-15 UAL2858 TPA → EWR Jul 15, 15:00 UTCJul 15, 17:20 UTC2h 20m
2026-07-15 UAL1979 EWR → TPA Jul 15, 11:15 UTCJul 15, 13:25 UTC2h 10m
2026-07-15 UAL1162 BQN → EWR Jul 15, 04:32 UTCJul 15, 07:54 UTC3h 22m
2026-07-14 UAL569 EWR → BQN Jul 14, 23:36 UTCJul 15, 02:45 UTC3h 9m
2026-07-14 UAL569 - Jul 14, 23:30 UTCJul 15, 00:10 UTC40m

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 N37553 page for operator, model, and routing details .

Mode-S A44981 frequently asked

What is Mode-S code A44981?
A44981 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N37553.
Where is Mode-S A44981 registered?
Mode-S code A44981 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 A44981 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 A44981, octal 51044601, decimal 10,766,721.
What flights does A44981 operate?
Mode-S A44981 has broadcast 20 distinct callsigns, including UAL1176, UAL638, UAL446, UAL699, UAL569.