Apparatus

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sensors Mode-S transponder

A10E21

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N16701 · BOEING 737-700 · operated by UNITED AIRLINES INC

Hex
A10E21
Octal
50207041
Decimal
10,554,913
Country
US
Tail
N16701
Type
B737
No current signal · last broadcast Jul 25, 03:35 UTC
Flights observed
335
Distinct callsigns
20
Country
US
Last broadcast
Jul 25, 03:35 UTC

Last known position

Most recent position reported by Mode-S A10E21.

Country allocation

The ICAO 24-bit address A10E21 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
UAL1106 - 8 2026-06-16
UAL2256 United Airlines 6 2026-06-20
UAL2612 - 5 2026-06-26
UAL1861 - 5 2026-07-14
UAL400 United Airlines 4 2026-04-16
UAL2016 - 4 2026-06-24
UAL1888 United Airlines 4 2026-07-23
UAL1860 - 4 2026-07-14
UAL1853 United Airlines 4 2026-05-28
UAL1852 United Airlines 4 2026-05-28
UAL1478 - 4 2026-07-05
UAL1477 - 4 2026-07-16
UAL1381 United Airlines 4 2026-07-23
UAL1304 - 4 2026-07-08
UAL743 United Airlines 3 2026-06-08
UAL632 - 3 2026-07-19
UAL532 United Airlines 3 2026-04-22
UAL410 - 3 2026-07-03
UAL2485 United Airlines 3 2026-06-12
UAL241 - 3 2026-07-04

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-25 UAL3888 AMA → IAH Jul 25, 03:20 UTCJul 25, 03:35 UTC15m
2026-07-24 UAL2072 EWR → ATL Jul 24, 22:30 UTCJul 25, 01:10 UTC2h 40m
2026-07-24 UAL1955 IAD → PHX Jul 24, 18:05 UTCJul 24, 21:05 UTC3h 0m
2026-07-23 UAL378 ORD → EWR Jul 23, 22:15 UTCJul 24, 16:10 UTC17h 55m
2026-07-23 UAL1888 LAX → EWR Jul 23, 18:15 UTCJul 23, 19:50 UTC1h 35m
2026-07-23 UAL1888 LAX → EWR Jul 23, 18:12 UTCJul 23, 19:38 UTC1h 26m
2026-07-23 UAL1381 IAH → SAN Jul 23, 15:25 UTCJul 23, 16:40 UTC1h 15m
2026-07-23 UAL2218 SJU → EWR Jul 23, 11:15 UTCJul 23, 12:30 UTC1h 15m
2026-07-23 UAL2218 SJU → EWR Jul 23, 11:14 UTCJul 23, 12:18 UTC1h 4m
2026-07-23 UAL1946 - Jul 23, 00:15 UTCJul 23, 01:15 UTC1h 0m
2026-07-22 UAL307 - Jul 22, 15:45 UTCJul 22, 22:10 UTC6h 25m
2026-07-22 UAL2465 IAD → PWM Jul 22, 13:10 UTCJul 22, 14:30 UTC1h 20m
2026-07-22 UAL2063 PHL → ORD Jul 22, 03:15 UTCJul 22, 04:10 UTC55m
2026-07-21 UAL2860 LGA → DEN Jul 21, 22:50 UTCJul 22, 00:20 UTC1h 30m
2026-07-21 UAL2860 LGA → DEN Jul 21, 22:46 UTCJul 22, 00:07 UTC1h 21m
2026-07-21 UAL1746 LIH → SFO Jul 21, 20:25 UTCJul 21, 21:45 UTC1h 20m
2026-07-21 UAL1746 LIH → SFO Jul 21, 20:14 UTCJul 21, 21:41 UTC1h 27m
2026-07-21 UAL503 RDU → EWR Jul 21, 16:20 UTCJul 21, 18:40 UTC2h 20m
2026-07-21 UAL1186 DFW → ORD Jul 21, 11:25 UTCJul 21, 12:15 UTC50m
2026-07-21 UAL1186 DFW → ORD Jul 21, 11:29 UTCJul 21, 13:11 UTC1h 42m
2026-07-20 UAL1316 EWR → MIA Jul 20, 23:10 UTCJul 21, 02:00 UTC2h 50m
2026-07-20 UAL2844 BWI → ORD Jul 20, 19:00 UTCJul 20, 21:10 UTC2h 10m
2026-07-20 UAL1502 EWR → ORD Jul 20, 17:10 UTCJul 20, 17:15 UTC5m
2026-07-20 UAL1502 EWR → ORD Jul 20, 14:20 UTCJul 20, 17:15 UTC2h 55m
2026-07-20 UAL1502 EWR → ORD Jul 20, 14:16 UTCJul 20, 16:52 UTC2h 36m
2026-07-19 UAL2410 MSY → SFO Jul 19, 22:15 UTCJul 20, 02:25 UTC4h 10m
2026-07-19 UAL1764 - Jul 19, 19:50 UTCJul 19, 20:50 UTC1h 0m
2026-07-19 UAL632 - Jul 19, 03:30 UTCJul 19, 04:30 UTC1h 0m
2026-07-18 UAL471 IAD → BOS Jul 18, 12:30 UTCJul 18, 15:30 UTC3h 0m
2026-07-17 UAL1869 - Jul 17, 22:20 UTCJul 18, 01:10 UTC2h 50m
2026-07-17 UAL1869 IAD → SAT Jul 17, 22:09 UTCJul 18, 01:09 UTC3h 0m
2026-07-17 UAL2344 AUS → IAD Jul 17, 17:20 UTCJul 17, 20:15 UTC2h 55m
2026-07-17 UAL637 - Jul 17, 13:00 UTCJul 17, 14:15 UTC1h 15m
2026-07-17 UAL637 IAD → AUS Jul 17, 12:48 UTCJul 17, 15:41 UTC2h 53m
2026-07-17 UAL641 ATL → IAD Jul 17, 09:45 UTCJul 17, 11:00 UTC1h 15m
2026-07-17 UAL2081 IAD → ATL Jul 17, 00:14 UTCJul 17, 01:29 UTC1h 15m
2026-07-16 UAL2607 - Jul 16, 19:20 UTCJul 16, 20:00 UTC40m
2026-07-16 UAL2066 IAD → PIT Jul 16, 17:12 UTCJul 16, 17:49 UTC37m
2026-07-16 UAL2066 - Jul 16, 17:20 UTCJul 16, 17:49 UTC30m
2026-07-16 UAL471 - Jul 16, 12:30 UTCJul 16, 15:25 UTC2h 55m
2026-07-16 UAL1477 - Jul 16, 00:05 UTCJul 16, 00:40 UTC35m
2026-07-15 UAL1381 - Jul 15, 19:40 UTCJul 15, 22:25 UTC2h 45m
2026-07-15 UAL2670 - Jul 15, 15:25 UTCJul 15, 18:15 UTC2h 50m
2026-07-15 UAL1409 - Jul 15, 10:05 UTCJul 15, 13:35 UTC3h 30m
2026-07-14 UAL2161 - Jul 14, 22:05 UTCJul 15, 01:35 UTC3h 29m
2026-07-14 UAL1860 - Jul 14, 18:00 UTCJul 14, 19:50 UTC1h 50m
2026-07-14 UAL1861 - Jul 14, 15:10 UTCJul 14, 16:55 UTC1h 45m
2026-07-14 UAL1859 - Jul 14, 10:20 UTCJul 14, 13:05 UTC2h 45m
2026-07-14 UAL8140 IAH → PIT Jul 14, 04:40 UTCJul 14, 07:05 UTC2h 25m
2026-07-14 UAL8140 IAH → PIT Jul 14, 04:50 UTCJul 14, 07:02 UTC2h 12m

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 N16701 page for operator, model, and routing details .

Mode-S A10E21 frequently asked

What is Mode-S code A10E21?
A10E21 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N16701.
Where is Mode-S A10E21 registered?
Mode-S code A10E21 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 A10E21 broadcasting right now?
No active broadcast right now. Last signal was Jul 25, 03:35 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A10E21, octal 50207041, decimal 10,554,913.
What flights does A10E21 operate?
Mode-S A10E21 has broadcast 20 distinct callsigns, including UAL1106, UAL2256, UAL2612, UAL1861, UAL400.