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sensors Mode-S transponder

4A2181

ICAO 24-bit transponder address · allocated to Romania

Currently assigned to YR-HLA · BOEING 737-800

Hex
4A2181
Octal
22420601
Decimal
4,858,241
Country
RO
Tail
YR-HLA
Type
B738
Broadcasting now · callsign HLJ2VV · 34,000 ft
Flights observed
138
Distinct callsigns
20
Country
RO
Last broadcast
1h ago

Current position

4A2181 is currently broadcasting. Map zoomed to live position.

Country allocation

The ICAO 24-bit address 4A2181 falls within the block assigned to Romania (RO) by ICAO Annex 10, Volume III. Every aircraft registered in Romania 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
HLJ2VV - 53 2026-07-12
HLJ4AB - 12 2026-07-13
HLJ2GJ - 12 2026-07-11
HLJ2EY - 11 2026-07-14
HLJ3BF - 8 2026-07-06
HLJ2JK - 4 2026-05-16
HLJ1025 - 4 2026-07-09
HLJ818F - 3 2026-04-28
HLJ6AJ - 3 2026-06-16
HLJ1GL - 3 2026-06-30
HLJ1AM - 3 2026-06-30
HLJ1024 - 3 2026-06-30
HLJ5QY - 2 2026-07-09
HLJ4YA - 2 2026-07-09
HLJ2TT - 2 2026-06-25
HLJ135 - 2 2026-06-30
HLJ134 - 2 2026-06-30
HLJ817F - 1 2026-04-24
HLJ814F - 1 2026-04-20
HLJ5CG - 1 2026-05-08

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-14 HLJ2EY - Jul 14, 05:55 UTCJul 14, 14:15 UTC8h 20m
2026-07-13 HLJ4AB PRG → PRG Jul 13, 05:50 UTCJul 13, 15:30 UTC9h 40m
2026-07-12 HLJ2VV PRG → PRG Jul 12, 05:10 UTCJul 12, 15:10 UTC10h 0m
2026-07-11 HLJ2GJ PRG → PRG Jul 11, 18:05 UTCJul 12, 03:45 UTC9h 40m
2026-07-11 HLJ2VV PRG → PRG Jul 11, 05:10 UTCJul 11, 15:00 UTC9h 50m
2026-07-10 HLJ2VV PRG → PRG Jul 10, 05:20 UTCJul 10, 15:10 UTC9h 50m
2026-07-09 HLJ1025 PRG → PRG Jul 9, 18:30 UTCJul 10, 03:55 UTC9h 25m
2026-07-09 HLJ4YA RHO → PRG Jul 9, 09:15 UTCJul 9, 12:00 UTC2h 45m
2026-07-09 HLJ5QY PRG → RHO Jul 9, 05:10 UTCJul 9, 07:30 UTC2h 20m
2026-07-08 HLJ2VV PRG → PRG Jul 8, 04:20 UTCJul 8, 14:15 UTC9h 55m
2026-07-07 HLJ2VV PRG → PRG Jul 7, 05:45 UTCJul 7, 15:40 UTC9h 55m
2026-07-06 HLJ3BF PRG → PRG Jul 6, 05:50 UTCJul 6, 15:35 UTC9h 45m
2026-07-05 HLJ2VV PRG → PRG Jul 5, 05:15 UTCJul 5, 15:10 UTC9h 55m
2026-07-04 HLJ2GJ PRG → PRG Jul 4, 17:30 UTCJul 5, 04:00 UTC10h 30m
2026-07-04 HLJ2VV PRG → PRG Jul 4, 05:15 UTCJul 4, 15:30 UTC10h 15m
2026-07-03 HLJ2VV PRG → PRG Jul 3, 05:35 UTCJul 3, 15:20 UTC9h 45m
2026-07-02 HLJ4AB PRG → PRG Jul 2, 18:45 UTCJul 3, 04:15 UTC9h 30m
2026-07-02 HLJ4YA RHO → PRG Jul 2, 09:35 UTCJul 2, 12:05 UTC2h 30m
2026-07-02 HLJ5QY PRG → RHO Jul 2, 05:15 UTCJul 2, 07:50 UTC2h 35m
2026-07-01 HLJ3BF PRG → PRG Jul 1, 05:20 UTCJul 1, 14:25 UTC9h 5m
2026-06-30 HLJ1024 PRG → PRG Jun 30, 17:50 UTCJul 1, 03:55 UTC10h 5m
2026-06-30 HLJ1AM - Jun 30, 14:10 UTCJun 30, 15:55 UTC1h 45m
2026-06-30 HLJ135 - Jun 30, 11:25 UTCJun 30, 13:15 UTC1h 50m
2026-06-30 HLJ134 - Jun 30, 08:10 UTCJun 30, 09:45 UTC1h 35m
2026-06-30 HLJ1GL PRG → BOJ Jun 30, 05:00 UTCJun 30, 07:00 UTC2h 0m
2026-06-29 HLJ4AB PRG → PRG Jun 29, 05:50 UTCJun 29, 15:14 UTC9h 25m
2026-06-28 HLJ2VV PRG → PRG Jun 28, 07:14 UTCJun 28, 16:49 UTC9h 35m
2026-06-27 HLJ2GJ PRG → PRG Jun 27, 17:49 UTCJun 28, 04:05 UTC10h 15m
2026-06-27 HLJ2VV PRG → PRG Jun 27, 05:15 UTCJun 27, 14:49 UTC9h 35m
2026-06-26 HLJ2VV PRG → PRG Jun 26, 05:19 UTCJun 26, 15:10 UTC9h 50m
2026-06-25 HLJ1UU - Jun 25, 17:34 UTCJun 26, 03:45 UTC10h 10m
2026-06-25 HLJ2TT PRG → PED Jun 25, 05:39 UTCJun 25, 15:34 UTC9h 55m
2026-06-23 HLJ1AM - Jun 23, 14:39 UTCJun 23, 16:29 UTC1h 50m
2026-06-23 HLJ135 PED → BOJ Jun 23, 11:49 UTCJun 23, 13:39 UTC1h 50m
2026-06-23 HLJ134 BOJ → PED Jun 23, 08:09 UTCJun 23, 09:54 UTC1h 45m
2026-06-23 HLJ1GL PRG → BOJ Jun 23, 05:15 UTCJun 23, 07:05 UTC1h 50m
2026-06-22 HLJ3BF PRG → PRG Jun 22, 05:49 UTCJun 22, 15:24 UTC9h 35m
2026-06-21 HLJ2VV PRG → PRG Jun 21, 07:20 UTCJun 21, 17:05 UTC9h 45m
2026-06-20 HLJ2GJ PRG → PRG Jun 20, 17:54 UTCJun 21, 04:49 UTC10h 55m
2026-06-20 HLJ2VV PRG → PRG Jun 20, 05:29 UTCJun 20, 15:29 UTC10h 0m
2026-06-19 HLJ2VV PRG → PRG Jun 19, 05:34 UTCJun 19, 15:24 UTC9h 50m
2026-06-18 HLJ2GJ PED → PRG Jun 18, 17:30 UTCJun 19, 03:55 UTC10h 24m
2026-06-18 HLJ2TT PRG → PED Jun 18, 05:50 UTCJun 18, 15:25 UTC9h 35m
2026-06-16 HLJ1025 - Jun 16, 23:45 UTCJun 17, 03:35 UTC3h 50m
2026-06-16 HLJ1024 - Jun 16, 17:49 UTCJun 16, 21:35 UTC3h 46m
2026-06-16 HLJ6AJ PRG → PRG Jun 16, 05:34 UTCJun 16, 13:25 UTC7h 50m
2026-06-15 HLJ2GJ PRG → PRG Jun 15, 17:45 UTCJun 16, 03:55 UTC10h 10m
2026-06-14 HLJ2VV PRG → PRG Jun 14, 07:20 UTCJun 14, 17:30 UTC10h 10m
2026-06-13 HLJ2GJ PRG → PRG Jun 13, 17:45 UTCJun 14, 04:20 UTC10h 35m
2026-06-13 HLJ2VV PRG → PRG Jun 13, 05:35 UTCJun 13, 15:30 UTC9h 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 YR-HLA page for operator, model, and routing details .

Mode-S 4A2181 frequently asked

What is Mode-S code 4A2181?
4A2181 is an ICAO 24-bit transponder address. Allocated to Romania. Assigned to YR-HLA.
Where is Mode-S 4A2181 registered?
Mode-S code 4A2181 is allocated to Romania (RO). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4A2181 broadcasting right now?
Yes. Mode-S 4A2181 is currently airborne.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4A2181, octal 22420601, decimal 4,858,241.
What flights does 4A2181 operate?
Mode-S 4A2181 has broadcast 20 distinct callsigns, including HLJ2VV, HLJ4AB, HLJ2GJ, HLJ2EY, HLJ3BF.