Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A4455E

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N37420 · BOEING 737-900 · operated by UNITED AIRLINES INC

Hex
A4455E
Octal
51042536
Decimal
10,765,662
Country
US
Tail
N37420
Type
B739
No current signal · last broadcast Jul 26, 21:30 UTC
Flights observed
474
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:30 UTC

Last known position

Most recent position reported by Mode-S A4455E.

Country allocation

The ICAO 24-bit address A4455E 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
UAL2215 United Airlines 6 2026-05-05
UAL1647 United Airlines 5 2026-07-17
UAL1018 - 5 2026-07-19
UAL728 United Airlines 4 2026-07-14
UAL2741 - 4 2026-07-03
UAL2120 United Airlines 4 2026-07-10
UAL1615 - 4 2026-07-02
UAL1392 United Airlines 4 2026-07-25
UAL1273 - 4 2026-07-03
UAL1051 United Airlines 4 2026-07-19
UAL776 United Airlines 3 2026-04-24
UAL703 United Airlines 3 2026-06-05
UAL663 United Airlines 3 2026-07-21
UAL457 United Airlines 3 2026-07-24
UAL284 United Airlines 3 2026-04-13
UAL2784 United Airlines 3 2026-07-24
UAL2649 United Airlines 3 2026-06-01
UAL2643 United Airlines 3 2026-06-09
UAL2640 United Airlines 3 2026-06-08
UAL2605 United Airlines 3 2026-06-09

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1800 SNA → IAH Jul 26, 20:30 UTCJul 26, 21:30 UTC1h 0m
2026-07-26 UAL677 ORD → BOS Jul 26, 15:55 UTCJul 26, 18:15 UTC2h 20m
2026-07-26 UAL1847 MIA → ORD Jul 26, 11:10 UTCJul 26, 14:15 UTC3h 5m
2026-07-26 UAL1847 MIA → ORD Jul 26, 11:13 UTCJul 26, 14:18 UTC3h 5m
2026-07-26 UAL2856 EWR → JAX Jul 26, 01:00 UTCJul 26, 03:55 UTC2h 55m
2026-07-25 UAL1206 SFO → DFW Jul 25, 21:05 UTCJul 25, 23:25 UTC2h 20m
2026-07-25 UAL2277 ORD → SAT Jul 25, 16:55 UTCJul 25, 18:55 UTC2h 0m
2026-07-25 UAL1392 EWR → CLT Jul 25, 13:10 UTCJul 25, 15:15 UTC2h 5m
2026-07-25 UAL1761 SAN → SFO Jul 25, 02:10 UTCJul 25, 04:00 UTC1h 50m
2026-07-24 UAL1673 CLE → ORD Jul 24, 23:15 UTCJul 25, 00:15 UTC1h 0m
2026-07-24 UAL1502 EWR → ORD Jul 24, 21:20 UTCJul 24, 22:05 UTC45m
2026-07-24 UAL2784 GUM → SFO Jul 24, 19:30 UTCJul 24, 19:35 UTC5m
2026-07-24 UAL2784 GUM → SFO Jul 24, 17:50 UTCJul 24, 19:30 UTC1h 40m
2026-07-24 UAL2784 GUM → SFO Jul 24, 17:45 UTCJul 24, 19:12 UTC1h 27m
2026-07-24 UAL2752 LAX → SFO Jul 24, 14:45 UTCJul 24, 16:20 UTC1h 35m
2026-07-24 UAL490 YYZ → ORD Jul 24, 11:10 UTCJul 24, 12:20 UTC1h 10m
2026-07-24 UAL457 BWI → SFO Jul 24, 03:00 UTCJul 24, 03:50 UTC50m
2026-07-23 UAL2311 IAH → RNO Jul 23, 22:20 UTCJul 24, 01:05 UTC2h 45m
2026-07-23 UAL1496 DEN → MIA Jul 23, 17:20 UTCJul 23, 21:05 UTC3h 45m
2026-07-23 UAL1765 SFO → DFW Jul 23, 12:40 UTCJul 23, 15:40 UTC3h 0m
2026-07-23 UAL8155 CDG → YYZ Jul 23, 00:10 UTCJul 23, 02:45 UTC2h 35m
2026-07-22 UAL2821 - Jul 22, 19:50 UTCJul 22, 22:35 UTC2h 45m
2026-07-22 UAL1522 FLL → EWR Jul 22, 16:25 UTCJul 22, 18:25 UTC2h 0m
2026-07-22 UAL557 - Jul 22, 13:00 UTCJul 22, 14:10 UTC1h 10m
2026-07-22 UAL1417 DEN → RDU Jul 22, 02:05 UTCJul 22, 03:10 UTC1h 5m
2026-07-21 UAL2288 IAH → LAS Jul 21, 21:00 UTCJul 22, 00:15 UTC3h 15m
2026-07-21 UAL2269 DEN → RDU Jul 21, 16:10 UTCJul 21, 18:55 UTC2h 45m
2026-07-21 UAL2185 MFR → DEN Jul 21, 12:15 UTCJul 21, 14:20 UTC2h 5m
2026-07-21 UAL663 DEN → ABQ Jul 21, 04:00 UTCJul 21, 04:10 UTC10m
2026-07-21 UAL663 DEN → ABQ Jul 21, 02:00 UTCJul 21, 03:30 UTC1h 30m
2026-07-20 UAL1773 MIA → EWR Jul 20, 20:34 UTCJul 20, 23:40 UTC3h 6m
2026-07-20 UAL1773 MIA → EWR Jul 20, 20:35 UTCJul 20, 23:50 UTC3h 15m
2026-07-20 UAL1834 DFW → EWR Jul 20, 16:40 UTCJul 20, 18:50 UTC2h 10m
2026-07-20 UAL1834 DFW → EWR Jul 20, 12:40 UTCJul 20, 14:50 UTC2h 10m
2026-07-20 UAL2058 EWR → BOS Jul 20, 02:20 UTCJul 20, 03:00 UTC40m
2026-07-19 UAL1051 CUN → EWR Jul 19, 18:30 UTCJul 19, 22:20 UTC3h 50m
2026-07-19 UAL1018 - Jul 19, 15:10 UTCJul 19, 15:30 UTC20m
2026-07-19 UAL1018 IAH → CUN Jul 19, 15:02 UTCJul 19, 17:00 UTC1h 58m
2026-07-19 UAL1859 - Jul 19, 10:25 UTCJul 19, 12:50 UTC2h 25m
2026-07-19 UAL1591 - Jul 19, 01:15 UTCJul 19, 03:35 UTC2h 20m
2026-07-18 UAL1516 LIR → IAH Jul 18, 19:56 UTCJul 18, 22:53 UTC2h 57m
2026-07-18 UAL1516 - Jul 18, 15:00 UTCJul 18, 23:00 UTC8h 0m
2026-07-18 UAL2425 EWR → MSY Jul 18, 01:43 UTCJul 18, 04:45 UTC3h 2m
2026-07-18 UAL2425 EWR → MSY Jul 18, 02:00 UTCJul 18, 04:50 UTC2h 51m
2026-07-17 UAL1647 IAH → MSY Jul 17, 23:20 UTCJul 18, 00:10 UTC50m
2026-07-17 UAL1536 EWR → BOS Jul 17, 19:48 UTCJul 17, 20:32 UTC44m
2026-07-17 UAL1536 EWR → BOS Jul 17, 19:40 UTCJul 17, 20:20 UTC40m
2026-07-17 UAL210 - Jul 17, 15:35 UTCJul 17, 18:00 UTC2h 25m
2026-07-17 UAL715 - Jul 17, 11:39 UTCJul 17, 14:04 UTC2h 25m
2026-07-16 UAL2725 - Jul 16, 21:15 UTCJul 16, 23:35 UTC2h 20m

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 N37420 page for operator, model, and routing details .

Mode-S A4455E frequently asked

What is Mode-S code A4455E?
A4455E is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N37420.
Where is Mode-S A4455E registered?
Mode-S code A4455E 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 A4455E broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:30 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A4455E, octal 51042536, decimal 10,765,662.
What flights does A4455E operate?
Mode-S A4455E has broadcast 20 distinct callsigns, including UAL2215, UAL1647, UAL1018, UAL728, UAL2741.