Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A39FB1

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N33203 · BOEING 737-800 · operated by UNITED AIRLINES INC

Hex
A39FB1
Octal
50717661
Decimal
10,723,249
Country
US
Tail
N33203
Type
B738
No current signal · last broadcast 3d ago
Flights observed
389
Distinct callsigns
20
Country
US
Last broadcast
3d ago

Last known position

Most recent position reported by Mode-S A39FB1.

Country allocation

The ICAO 24-bit address A39FB1 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
UAL2299 - 6 2026-06-25
UAL2189 - 5 2026-06-25
UAL1501 United Airlines 5 2026-06-12
UAL488 United Airlines 4 2026-05-07
UAL467 United Airlines 4 2026-06-09
UAL2306 - 4 2026-07-10
UAL691 United Airlines 3 2026-05-28
UAL680 - 3 2026-07-02
UAL645 - 3 2026-06-17
UAL635 United Airlines 3 2026-05-12
UAL547 United Airlines 3 2026-05-26
UAL464 United Airlines 3 2026-04-15
UAL414 - 3 2026-07-05
UAL286 United Airlines 3 2026-04-23
UAL2745 - 3 2026-07-04
UAL2271 - 3 2026-06-30
UAL2239 United Airlines 3 2026-04-15
UAL2174 United Airlines 3 2026-05-07
UAL2144 United Airlines 3 2026-04-28
UAL202 - 3 2026-07-07

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-11 UAL3881 CLE → IAB Jul 11, 03:45 UTCJul 11, 05:34 UTC1h 49m
2026-07-11 UAL3881 - Jul 11, 03:15 UTCJul 11, 03:25 UTC10m
2026-07-11 UAL1641 ORD → CLE Jul 11, 01:35 UTCJul 11, 02:20 UTC45m
2026-07-10 UAL2059 ROC → ORD Jul 10, 22:14 UTCJul 10, 23:45 UTC1h 31m
2026-07-10 UAL2059 ROC → ORD Jul 10, 22:10 UTCJul 10, 23:45 UTC1h 35m
2026-07-10 UAL1239 ORD → ROC Jul 10, 19:30 UTCJul 10, 20:35 UTC1h 5m
2026-07-10 UAL1239 ATL → ORD Jul 10, 16:05 UTCJul 10, 17:45 UTC1h 40m
2026-07-10 UAL425 - Jul 10, 12:55 UTCJul 10, 14:45 UTC1h 50m
2026-07-10 UAL1830 LGA → ORD Jul 10, 05:30 UTCJul 10, 07:25 UTC1h 55m
2026-07-10 UAL1830 LGA → ORD Jul 10, 05:21 UTCJul 10, 07:12 UTC1h 51m
2026-07-10 UAL2306 - Jul 10, 02:30 UTCJul 10, 04:05 UTC1h 35m
2026-07-10 UAL2306 ORD → LGA Jul 10, 01:51 UTCJul 10, 04:03 UTC2h 12m
2026-07-09 UAL1398 COS → ORD Jul 9, 18:28 UTCJul 9, 20:02 UTC1h 34m
2026-07-09 UAL1398 COS → ORD Jul 9, 18:15 UTCJul 9, 20:15 UTC2h 0m
2026-07-09 UAL1082 - Jul 9, 14:30 UTCJul 9, 16:55 UTC2h 25m
2026-07-09 UAL1830 LGA → ORD Jul 9, 01:35 UTCJul 9, 03:20 UTC1h 45m
2026-07-08 UAL2306 - Jul 8, 22:55 UTCJul 9, 00:35 UTC1h 40m
2026-07-08 UAL1398 - Jul 8, 18:30 UTCJul 8, 20:30 UTC2h 0m
2026-07-08 UAL1082 DPA → COS Jul 8, 14:40 UTCJul 8, 16:40 UTC2h 0m
2026-07-08 UAL1621 MCO → ORD Jul 8, 00:15 UTCJul 8, 02:35 UTC2h 20m
2026-07-07 UAL1811 ORD → MCO Jul 7, 18:05 UTCJul 7, 20:15 UTC2h 10m
2026-07-07 UAL202 AUS → ORD Jul 7, 13:35 UTCJul 7, 15:50 UTC2h 15m
2026-07-07 UAL1179 - Jul 7, 03:40 UTCJul 7, 04:10 UTC30m
2026-07-06 UAL2217 - Jul 6, 22:50 UTCJul 7, 01:35 UTC2h 45m
2026-07-06 UAL1140 LAS → IAD Jul 6, 15:55 UTCJul 6, 20:10 UTC4h 15m
2026-07-06 UAL582 - Jul 6, 13:10 UTCJul 6, 14:20 UTC1h 10m
2026-07-06 UAL582 SFO → LAS Jul 6, 13:19 UTCJul 6, 14:19 UTC1h 0m
2026-07-06 UAL1273 DFW → SFO Jul 6, 02:50 UTCJul 6, 06:15 UTC3h 25m
2026-07-05 UAL414 DEN → DFW Jul 5, 22:00 UTCJul 5, 23:50 UTC1h 50m
2026-07-05 UAL414 DEN → DFW Jul 5, 22:01 UTCJul 5, 23:38 UTC1h 37m
2026-07-05 UAL1195 - Jul 5, 19:05 UTCJul 5, 20:15 UTC1h 10m
2026-07-05 UAL361 - Jul 5, 16:25 UTCJul 5, 17:25 UTC1h 0m
2026-07-04 UAL1362 - Jul 4, 19:40 UTCJul 5, 13:50 UTC18h 10m
2026-07-04 UAL586 SJC → DEN Jul 4, 15:55 UTCJul 4, 18:05 UTC2h 10m
2026-07-04 UAL2745 DEN → SJC Jul 4, 02:30 UTCJul 4, 04:35 UTC2h 5m
2026-07-03 UAL2108 LAS → DEN Jul 3, 23:45 UTCJul 4, 01:25 UTC1h 40m
2026-07-03 UAL2108 LAS → DEN Jul 3, 23:46 UTCJul 4, 01:11 UTC1h 25m
2026-07-03 UAL2156 IAH → SFO Jul 3, 17:20 UTCJul 3, 21:45 UTC4h 25m
2026-07-03 UAL2098 BOS → IAD Jul 3, 13:40 UTCJul 3, 14:50 UTC1h 10m
2026-07-02 UAL2798 DEN → BOS Jul 2, 22:40 UTCJul 3, 02:05 UTC3h 25m
2026-07-02 UAL1396 - Jul 2, 19:45 UTCJul 2, 20:30 UTC45m
2026-07-02 UAL1217 DEN → DRO Jul 2, 17:37 UTCJul 2, 18:10 UTC33m
2026-07-02 UAL1217 - Jul 2, 17:30 UTCJul 2, 18:05 UTC35m
2026-07-02 UAL2270 ORF → DEN Jul 2, 12:05 UTCJul 2, 15:35 UTC3h 30m
2026-07-02 UAL680 DEN → ORF Jul 2, 00:25 UTCJul 2, 03:25 UTC3h 0m
2026-07-01 UAL1534 - Jul 1, 21:00 UTCJul 1, 22:45 UTC1h 45m
2026-07-01 UAL2167 - Jul 1, 17:35 UTCJul 1, 18:55 UTC1h 20m
2026-07-01 UAL2750 - Jul 1, 12:00 UTCJul 1, 15:40 UTC3h 40m
2026-07-01 UAL8125 DEN → ALB Jul 1, 00:10 UTCJul 1, 03:10 UTC3h 0m
2026-07-01 UAL8125 DEN → ALB Jul 1, 00:05 UTCJul 1, 03:07 UTC3h 2m

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 N33203 page for operator, model, and routing details .

Mode-S A39FB1 frequently asked

What is Mode-S code A39FB1?
A39FB1 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N33203.
Where is Mode-S A39FB1 registered?
Mode-S code A39FB1 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 A39FB1 broadcasting right now?
No active broadcast right now. Last signal was 3d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A39FB1, octal 50717661, decimal 10,723,249.
What flights does A39FB1 operate?
Mode-S A39FB1 has broadcast 20 distinct callsigns, including UAL2299, UAL2189, UAL1501, UAL488, UAL467.