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
Broadcasting now · callsign UAL1457 · 275 ft
Flights observed
450
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 19:20 UTC

Current position

A39FB1 is currently broadcasting. Map zoomed to live position.

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
UAL2306 United Airlines 6 2026-07-22
UAL2299 - 6 2026-06-25
UAL691 United Airlines 5 2026-07-23
UAL2189 - 5 2026-06-25
UAL1501 United Airlines 5 2026-06-12
UAL719 United Airlines 4 2026-07-25
UAL645 United Airlines 4 2026-07-21
UAL488 United Airlines 4 2026-05-07
UAL467 United Airlines 4 2026-06-09
UAL2668 United Airlines 4 2026-07-17
UAL694 - 3 2026-07-16
UAL680 - 3 2026-07-02
UAL635 United Airlines 3 2026-05-12
UAL586 United Airlines 3 2026-07-24
UAL547 United Airlines 3 2026-05-26
UAL464 United Airlines 3 2026-04-15
UAL414 - 3 2026-07-05
UAL372 - 3 2026-07-15
UAL286 United Airlines 3 2026-04-23
UAL2745 - 3 2026-07-04

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL245 BZN → EWR Jul 26, 14:55 UTCJul 26, 19:00 UTC4h 5m
2026-07-26 UAL2281 CVG → IAH Jul 26, 12:05 UTCJul 26, 13:10 UTC1h 5m
2026-07-26 UAL2236 SFO → BOS Jul 26, 01:50 UTCJul 26, 02:50 UTC1h 0m
2026-07-25 UAL1696 SFO → RNO Jul 25, 21:35 UTCJul 25, 23:45 UTC2h 10m
2026-07-25 UAL2188 DEN → FLL Jul 25, 16:25 UTCJul 25, 20:05 UTC3h 40m
2026-07-25 UAL2188 DEN → FLL Jul 25, 16:08 UTCJul 25, 19:48 UTC3h 40m
2026-07-25 UAL225 ATL → DEN Jul 25, 12:50 UTCJul 25, 14:30 UTC1h 40m
2026-07-25 UAL225 ATL → DEN Jul 25, 12:43 UTCJul 25, 14:29 UTC1h 46m
2026-07-25 UAL719 MIA → EWR Jul 25, 03:35 UTCJul 25, 03:45 UTC10m
2026-07-25 UAL719 MIA → EWR Jul 25, 01:50 UTCJul 25, 03:05 UTC1h 15m
2026-07-24 UAL2123 AUS → SFO Jul 24, 23:05 UTCJul 25, 00:40 UTC1h 35m
2026-07-24 UAL586 DEN → MCI Jul 24, 20:45 UTCJul 24, 21:45 UTC1h 0m
2026-07-24 UAL2789 GUM → SFO Jul 24, 14:50 UTCJul 24, 15:55 UTC1h 5m
2026-07-24 UAL2166 TPA → SFO Jul 24, 01:50 UTCJul 24, 02:45 UTC55m
2026-07-23 UAL725 ORD → SFO Jul 23, 23:40 UTCJul 24, 00:40 UTC1h 0m
2026-07-23 UAL691 ORD → IAH Jul 23, 20:09 UTCJul 23, 21:00 UTC51m
2026-07-23 UAL691 ORD → IAH Jul 23, 20:10 UTCJul 23, 21:05 UTC55m
2026-07-23 UAL2375 PHL → ORD Jul 23, 16:00 UTCJul 23, 18:05 UTC2h 5m
2026-07-22 UAL1677 SFO → DFW Jul 22, 22:45 UTCJul 23, 02:35 UTC3h 50m
2026-07-22 UAL2306 ORD → BOS Jul 22, 14:05 UTCJul 22, 17:15 UTC3h 10m
2026-07-22 UAL2306 ORD → BOS Jul 22, 14:12 UTCJul 22, 17:09 UTC2h 57m
2026-07-21 UAL1337 EWR → PDX Jul 21, 22:20 UTCJul 22, 00:35 UTC2h 15m
2026-07-21 UAL645 LAX → EWR Jul 21, 16:55 UTCJul 21, 20:05 UTC3h 10m
2026-07-21 UAL683 IAD → TPA Jul 21, 13:21 UTCJul 21, 15:13 UTC1h 52m
2026-07-21 UAL683 IAD → TPA Jul 21, 13:20 UTCJul 21, 15:15 UTC1h 55m
2026-07-21 UAL1997 MCO → IAD Jul 21, 00:35 UTCJul 21, 02:50 UTC2h 15m
2026-07-20 UAL1101 IAD → MCO Jul 20, 20:30 UTCJul 20, 22:15 UTC1h 45m
2026-07-20 UAL2054 RSW → IAD Jul 20, 16:20 UTCJul 20, 18:25 UTC2h 5m
2026-07-20 UAL1406 IAD → RSW Jul 20, 12:33 UTCJul 20, 14:29 UTC1h 56m
2026-07-20 UAL1406 IAD → RSW Jul 20, 12:30 UTCJul 20, 14:35 UTC2h 5m
2026-07-19 UAL2382 IAH → PHL Jul 19, 23:50 UTCJul 20, 04:00 UTC4h 10m
2026-07-19 UAL1799 MIA → EWR Jul 19, 17:45 UTCJul 19, 20:10 UTC2h 25m
2026-07-19 UAL2141 - Jul 19, 14:10 UTCJul 19, 15:25 UTC1h 15m
2026-07-19 UAL2109 - Jul 19, 01:25 UTCJul 19, 02:30 UTC1h 5m
2026-07-19 UAL2109 IAH → GDL Jul 19, 01:27 UTCJul 19, 03:12 UTC1h 45m
2026-07-18 UAL1601 - Jul 18, 21:20 UTCJul 18, 23:05 UTC1h 45m
2026-07-18 UAL1600 - Jul 18, 18:05 UTCJul 18, 19:45 UTC1h 40m
2026-07-18 UAL1957 PHL → IAH Jul 18, 13:10 UTCJul 18, 16:25 UTC3h 15m
2026-07-18 UAL8123 - Jul 18, 01:54 UTCJul 18, 03:35 UTC1h 41m
2026-07-17 UAL1325 DCA → ORD Jul 17, 22:15 UTCJul 17, 23:55 UTC1h 40m
2026-07-17 UAL1325 DCA → ORD Jul 17, 22:05 UTCJul 17, 23:45 UTC1h 40m
2026-07-17 UAL2668 OMA → ORD Jul 17, 19:30 UTCJul 17, 19:35 UTC5m
2026-07-17 UAL2668 OMA → ORD Jul 17, 17:59 UTCJul 17, 19:13 UTC1h 14m
2026-07-17 UAL2668 OMA → ORD Jul 17, 17:55 UTCJul 17, 19:35 UTC1h 40m
2026-07-17 UAL763 - Jul 17, 13:35 UTCJul 17, 14:44 UTC1h 10m
2026-07-17 UAL436 - Jul 17, 07:40 UTCJul 17, 11:55 UTC4h 15m
2026-07-17 UAL2854 BUR → SFO Jul 17, 05:15 UTCJul 17, 06:10 UTC55m
2026-07-17 UAL2854 BUR → SFO Jul 17, 05:03 UTCJul 17, 06:05 UTC1h 2m
2026-07-17 UAL1321 MIA → EWR Jul 17, 03:25 UTCJul 17, 04:14 UTC50m
2026-07-16 UAL1174 - Jul 16, 23:29 UTCJul 17, 00:55 UTC1h 25m

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?
Yes. Mode-S A39FB1 is currently airborne.
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 UAL2306, UAL2299, UAL691, UAL2189, UAL1501.