Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A1BFB2

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N21108 · BOEING 757-200 · operated by UNITED AIRLINES INC

Hex
A1BFB2
Octal
50337662
Decimal
10,600,370
Country
US
Tail
N21108
Type
B752
No current signal · last broadcast 12d ago
Flights observed
215
Distinct callsigns
20
Country
US
Last broadcast
12d ago

Last known position

Most recent position reported by Mode-S A1BFB2.

Country allocation

The ICAO 24-bit address A1BFB2 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
UAL419 - 11 2026-07-01
UAL1558 - 8 2026-06-24
UAL1197 United Airlines 7 2026-05-15
UAL316 - 6 2026-06-29
UAL289 - 5 2026-06-23
UAL288 - 5 2026-06-22
UAL2445 United Airlines 5 2026-05-11
UAL2308 United Airlines 5 2026-05-20
UAL1981 United Airlines 5 2026-05-12
UAL1759 United Airlines 5 2026-05-18
UAL1283 United Airlines 5 2026-04-30
UAL978 - 4 2026-06-16
UAL317 - 4 2026-06-29
UAL282 United Airlines 4 2026-06-06
UAL2641 United Airlines 4 2026-06-17
UAL2381 United Airlines 4 2026-05-20
UAL2307 United Airlines 4 2026-05-19
UAL1343 United Airlines 4 2026-04-14
UAL119 United Airlines 4 2026-06-22
UAL913 - 3 2026-06-21

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-01 UAL3883 - Jul 1, 20:40 UTCJul 1, 22:30 UTC1h 50m
2026-07-01 UAL3883 EWR → PNS Jul 1, 20:32 UTCJul 1, 22:51 UTC2h 19m
2026-07-01 UAL419 SFO → EWR Jul 1, 13:30 UTCJul 1, 18:50 UTC5h 20m
2026-06-30 UAL1340 EWR → SFO Jun 30, 21:15 UTCJul 1, 02:55 UTC5h 40m
2026-06-30 UAL239 OPO → EWR Jun 30, 08:25 UTCJun 30, 15:12 UTC6h 47m
2026-06-30 UAL239 - Jun 30, 08:10 UTCJun 30, 14:30 UTC6h 20m
2026-06-29 UAL238 - Jun 29, 23:25 UTCJun 30, 05:40 UTC6h 16m
2026-06-29 UAL316 - Jun 29, 13:04 UTCJun 29, 18:30 UTC5h 25m
2026-06-29 UAL316 DUB → EWR Jun 29, 12:56 UTCJun 29, 19:55 UTC6h 59m
2026-06-29 UAL317 EWR → DUB Jun 29, 04:32 UTCJun 29, 10:08 UTC5h 36m
2026-06-29 UAL317 - Jun 29, 04:14 UTCJun 29, 05:54 UTC1h 40m
2026-06-28 UAL2227 - Jun 28, 19:29 UTCJun 29, 00:14 UTC4h 45m
2026-06-28 UAL2434 - Jun 28, 11:50 UTCJun 28, 16:49 UTC5h 0m
2026-06-28 UAL327 - Jun 28, 04:35 UTCJun 28, 09:05 UTC4h 30m
2026-06-27 UAL210 EWR → SAN Jun 27, 21:10 UTCJun 28, 02:39 UTC5h 30m
2026-06-27 UAL1149 EWR → SRQ Jun 27, 14:14 UTCJun 27, 18:54 UTC4h 40m
2026-06-26 UAL1340 - Jun 26, 21:35 UTCJun 27, 03:44 UTC6h 10m
2026-06-26 UAL145 - Jun 26, 12:00 UTCJun 26, 12:29 UTC30m
2026-06-26 UAL145 OPO → EWR Jun 26, 12:05 UTCJun 26, 19:14 UTC7h 9m
2026-06-26 UAL144 - Jun 26, 02:09 UTCJun 26, 08:10 UTC6h 0m
2026-06-25 UAL274 SFO → EWR Jun 25, 18:45 UTCJun 25, 23:19 UTC4h 35m
2026-06-24 UAL648 - Jun 24, 19:44 UTCJun 25, 01:35 UTC5h 50m
2026-06-24 UAL419 SFO → EWR Jun 24, 13:30 UTCJun 24, 18:15 UTC4h 45m
2026-06-24 UAL1558 EWR → SFO Jun 24, 00:25 UTCJun 24, 06:10 UTC5h 45m
2026-06-23 UAL2812 ORD → EWR Jun 23, 21:16 UTCJun 23, 22:35 UTC1h 19m
2026-06-23 UAL2812 ORD → EWR Jun 23, 21:05 UTCJun 23, 22:40 UTC1h 35m
2026-06-23 UAL289 - Jun 23, 08:35 UTCJun 23, 16:24 UTC7h 50m
2026-06-22 UAL288 ORD → SNN Jun 22, 23:47 UTCJun 23, 06:12 UTC6h 25m
2026-06-22 UAL288 - Jun 22, 23:55 UTCJun 23, 06:09 UTC6h 15m
2026-06-22 UAL119 ORD → EDI Jun 22, 10:44 UTCJun 22, 19:00 UTC8h 15m
2026-06-22 UAL118 ORD → EDI Jun 22, 00:20 UTCJun 22, 07:19 UTC7h 0m
2026-06-21 UAL913 KEF → ORD Jun 21, 12:29 UTCJun 21, 18:29 UTC6h 0m
2026-06-21 UAL913 KEF → ORD Jun 21, 12:29 UTCJun 21, 18:15 UTC5h 46m
2026-06-21 UAL913 - Jun 21, 12:19 UTCJun 21, 12:24 UTC5m
2026-06-21 UAL398 - Jun 21, 03:30 UTCJun 21, 04:30 UTC1h 0m
2026-06-21 UAL398 IAD → KEF Jun 21, 03:23 UTCJun 21, 08:57 UTC5h 34m
2026-06-20 UAL311 DUB → IAD Jun 20, 08:05 UTCJun 20, 15:39 UTC7h 35m
2026-06-19 UAL310 IAD → DUB Jun 19, 23:49 UTCJun 20, 05:58 UTC6h 9m
2026-06-19 UAL310 IAD → DUB Jun 19, 23:49 UTCJun 20, 06:05 UTC6h 15m
2026-06-19 UAL229 DUB → IAD Jun 19, 12:49 UTCJun 19, 20:14 UTC7h 25m
2026-06-19 UAL229 DUB → IAD Jun 19, 12:51 UTCJun 19, 20:11 UTC7h 20m
2026-06-19 UAL317 - Jun 19, 03:44 UTCJun 19, 09:40 UTC5h 55m
2026-06-18 UAL2227 - Jun 18, 19:25 UTCJun 18, 23:55 UTC4h 30m
2026-06-17 UAL2641 SFO → SAN Jun 17, 22:05 UTCJun 18, 03:20 UTC5h 15m
2026-06-17 UAL316 DUB → EWR Jun 17, 13:46 UTCJun 17, 20:19 UTC6h 33m
2026-06-17 UAL316 DUB → EWR Jun 17, 13:46 UTCJun 17, 20:06 UTC6h 20m
2026-06-17 UAL316 - Jun 17, 13:35 UTCJun 17, 14:25 UTC50m
2026-06-17 UAL228 IAD → DUB Jun 17, 05:30 UTCJun 17, 11:35 UTC6h 5m
2026-06-16 UAL979 EDI → IAD Jun 16, 20:25 UTCJun 17, 03:45 UTC7h 20m
2026-06-16 UAL978 IAD → EDI Jun 16, 12:30 UTCJun 16, 18:52 UTC6h 22m

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 N21108 page for operator, model, and routing details .

Mode-S A1BFB2 frequently asked

What is Mode-S code A1BFB2?
A1BFB2 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N21108.
Where is Mode-S A1BFB2 registered?
Mode-S code A1BFB2 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 A1BFB2 broadcasting right now?
No active broadcast right now. Last signal was 12d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1BFB2, octal 50337662, decimal 10,600,370.
What flights does A1BFB2 operate?
Mode-S A1BFB2 has broadcast 20 distinct callsigns, including UAL419, UAL1558, UAL1197, UAL316, UAL289.