Apparatus

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sensors Mode-S transponder

A12777

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N17355 · operated by UNITED AIRLINES INC

Hex
A12777
Octal
50223567
Decimal
10,561,399
Country
US
Tail
N17355
Type
B38M
No current signal · last broadcast Jul 26, 20:55 UTC
Flights observed
478
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 20:55 UTC

Last known position

Most recent position reported by Mode-S A12777.

Country allocation

The ICAO 24-bit address A12777 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
UAL1632 United Airlines 7 2026-05-31
UAL1138 United Airlines 7 2026-06-01
UAL513 - 5 2026-07-19
UAL226 - 5 2026-07-16
UAL1975 - 5 2026-06-21
UAL1959 - 5 2026-06-26
UAL1910 United Airlines 5 2026-04-16
UAL1676 United Airlines 5 2026-04-27
UAL1579 - 5 2026-07-04
UAL783 - 4 2026-07-04
UAL518 United Airlines 4 2026-05-27
UAL280 - 4 2026-07-01
UAL2656 - 4 2026-07-16
UAL2478 - 4 2026-06-18
UAL2231 - 4 2026-07-16
UAL1968 - 4 2026-04-13
UAL1789 United Airlines 4 2026-07-23
UAL1753 United Airlines 4 2026-06-22
UAL1523 United Airlines 4 2026-07-24
UAL1295 United Airlines 4 2026-06-01

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1311 EWR → CLT Jul 26, 19:40 UTCJul 26, 20:55 UTC1h 15m
2026-07-26 UAL1413 EWR → PBI Jul 26, 13:20 UTCJul 26, 18:05 UTC4h 45m
2026-07-26 UAL400 AUS → IAD Jul 26, 02:50 UTCJul 26, 07:45 UTC4h 56m
2026-07-26 UAL400 AUS → IAD Jul 26, 02:45 UTCJul 26, 07:44 UTC4h 59m
2026-07-25 UAL2649 ORD → LAX Jul 25, 23:10 UTCJul 26, 01:05 UTC1h 55m
2026-07-25 UAL1707 SXM → ORD Jul 25, 19:45 UTCJul 25, 21:35 UTC1h 50m
2026-07-25 UAL784 SBA → SFO Jul 25, 14:40 UTCJul 25, 17:50 UTC3h 10m
2026-07-24 UAL1566 IAD → MEX Jul 24, 22:10 UTCJul 25, 01:40 UTC3h 30m
2026-07-24 UAL1566 IAD → MEX Jul 24, 21:54 UTCJul 25, 02:14 UTC4h 20m
2026-07-24 UAL2344 IAH → CLE Jul 24, 17:25 UTCJul 24, 20:30 UTC3h 5m
2026-07-24 UAL637 MSY → DEN Jul 24, 13:15 UTCJul 24, 16:00 UTC2h 45m
2026-07-24 UAL1562 GUA → IAD Jul 24, 06:15 UTCJul 24, 10:00 UTC3h 45m
2026-07-24 UAL1523 IAD → GUA Jul 24, 02:15 UTCJul 24, 02:25 UTC10m
2026-07-23 UAL1523 IAD → GUA Jul 23, 22:45 UTCJul 24, 01:40 UTC2h 55m
2026-07-23 UAL2250 IAH → SAT Jul 23, 18:15 UTCJul 23, 21:15 UTC3h 0m
2026-07-23 UAL2250 IAH → SAT Jul 23, 18:13 UTCJul 23, 21:12 UTC2h 59m
2026-07-23 UAL1789 DEN → SJC Jul 23, 13:05 UTCJul 23, 16:00 UTC2h 55m
2026-07-23 UAL1562 GUA → IAD Jul 23, 06:20 UTCJul 23, 10:05 UTC3h 45m
2026-07-22 UAL1523 IAD → GUA Jul 22, 22:35 UTCJul 23, 02:30 UTC3h 55m
2026-07-22 UAL1523 IAD → GUA Jul 22, 22:25 UTCJul 23, 02:20 UTC3h 55m
2026-07-22 UAL2463 ORD → MCO Jul 22, 15:35 UTCJul 22, 19:40 UTC4h 5m
2026-07-21 UAL1550 IAD → EWR Jul 21, 23:25 UTCJul 22, 01:25 UTC2h 0m
2026-07-21 UAL1348 IAD → RDU Jul 21, 15:50 UTCJul 21, 18:00 UTC2h 10m
2026-07-21 UAL2820 IAH → SFO Jul 21, 01:45 UTCJul 21, 05:50 UTC4h 5m
2026-07-20 UAL1009 EWR → MCO Jul 20, 19:48 UTCJul 20, 23:26 UTC3h 38m
2026-07-20 UAL1009 EWR → MCO Jul 20, 19:45 UTCJul 20, 23:45 UTC4h 0m
2026-07-20 UAL1008 - Jul 20, 14:15 UTCJul 20, 17:50 UTC3h 35m
2026-07-20 UAL660 - Jul 20, 10:05 UTCJul 20, 11:45 UTC1h 40m
2026-07-20 UAL660 PHL → ORD Jul 20, 10:14 UTCJul 20, 11:30 UTC1h 16m
2026-07-20 UAL1744 IAD → ORD Jul 20, 03:40 UTCJul 20, 05:10 UTC1h 30m
2026-07-19 UAL1352 IAH → CMH Jul 19, 21:25 UTCJul 20, 01:05 UTC3h 40m
2026-07-19 UAL1320 SFO → ONT Jul 19, 17:42 UTCJul 19, 19:20 UTC1h 38m
2026-07-19 UAL1320 SFO → ONT Jul 19, 17:35 UTCJul 19, 19:20 UTC1h 45m
2026-07-19 UAL513 LGA → DEN Jul 19, 12:30 UTCJul 19, 16:00 UTC3h 30m
2026-07-19 UAL3922 IAD → LGA Jul 19, 10:40 UTCJul 19, 11:20 UTC40m
2026-07-18 UAL2092 - Jul 18, 13:40 UTCJul 18, 16:40 UTC3h 0m
2026-07-18 UAL450C SFO → DEN Jul 18, 04:18 UTCJul 18, 09:29 UTC5h 11m
2026-07-18 UAL450C SFO → DEN Jul 18, 04:10 UTCJul 18, 05:00 UTC50m
2026-07-17 UAL2369 - Jul 17, 19:35 UTCJul 18, 02:09 UTC6h 35m
2026-07-17 UAL700 - Jul 17, 14:50 UTCJul 17, 17:44 UTC2h 55m
2026-07-17 UAL700 IAH → EWR Jul 17, 15:00 UTCJul 17, 17:45 UTC2h 45m
2026-07-17 UAL2761 - Jul 17, 01:39 UTCJul 17, 04:35 UTC2h 55m
2026-07-16 UAL2230 - Jul 16, 21:15 UTCJul 16, 23:35 UTC2h 20m
2026-07-16 UAL2231 - Jul 16, 17:10 UTCJul 16, 19:20 UTC2h 10m
2026-07-16 UAL2231 IAH → NAS Jul 16, 17:12 UTCJul 16, 19:18 UTC2h 6m
2026-07-16 UAL226 BOS → IAH Jul 16, 11:42 UTCJul 16, 14:53 UTC3h 11m
2026-07-16 UAL226 - Jul 16, 11:40 UTCJul 16, 15:00 UTC3h 20m
2026-07-16 UAL2656 DEN → BOS Jul 16, 06:15 UTCJul 16, 09:45 UTC3h 30m
2026-07-16 UAL2656 - Jul 16, 01:35 UTCJul 16, 03:30 UTC1h 55m
2026-07-15 UAL2657 - Jul 15, 22:25 UTCJul 16, 00:20 UTC1h 55m

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 N17355 page for operator, model, and routing details .

Mode-S A12777 frequently asked

What is Mode-S code A12777?
A12777 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N17355.
Where is Mode-S A12777 registered?
Mode-S code A12777 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 A12777 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 20:55 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A12777, octal 50223567, decimal 10,561,399.
What flights does A12777 operate?
Mode-S A12777 has broadcast 20 distinct callsigns, including UAL1632, UAL1138, UAL513, UAL226, UAL1975.