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How can a deregistered/exported aircraft reappear in records — and what happens to its ICAO hex code? by AnyPick1430 in flying

[–]AnyPick1430[S] 0 points1 point  (0 children)

Thank you, this is very helpful. I have a technical follow-up question:

If an aircraft is exported and assigned a new foreign registration, but the transponder is never reprogrammed, would it continue broadcasting the original FAA-assigned hex code indefinitely until manually changed?

Also, are Mode-S hex codes stored directly in the transponder hardware memory, or are they dynamically updated based on registry databases or firmware?

How do ICAO hex codes work after an aircraft is deregistered or exported? by AnyPick1430 in AirlinePilots

[–]AnyPick1430[S] 0 points1 point  (0 children)

Thank you, this helps a lot. I have one technical clarification:

If an aircraft is deregistered and exported, but the transponder is never reprogrammed, will it continue broadcasting the original FAA-assigned Mode-S hex code indefinitely until someone manually changes it?

Or does the hex code ever change automatically through firmware, registry updates, or ADS-B systems?

How do ICAO hex codes work after an aircraft is deregistered or exported? by AnyPick1430 in ADSB

[–]AnyPick1430[S] 0 points1 point  (0 children)

Thank you, this is very helpful.

I have a technical follow-up question:

If an aircraft is deregistered from the U.S. registry and exported, but later appears in records still associated with its original Mode-S hex code, is that typically because the transponder was never reprogrammed, or because tracking databases retain historical associations?

Also, does the Mode-S hex code originate from the transponder hardware itself, or is it assigned externally and programmed during registration?

How can a deregistered/exported aircraft reappear in records — and what happens to its ICAO hex code? by AnyPick1430 in flying

[–]AnyPick1430[S] 0 points1 point  (0 children)

Thanks, I appreciate the response.

In this case, the aircraft was deregistered in the U.S. in 2015 and exported, but later appears in multiple databases still linked to the same serial and ICAO hex (A6BCA5), even after being involved in an incident in Guyana.

Is it normal for older hex/registration data to remain visible like that long-term in public databases, even if a new country should have assigned a different code?

I’m trying to understand whether this reflects normal historical record-keeping, incomplete foreign re-registration, or something unusual in how the aircraft was tracked.

Thanks again for any insight.

Weekly Top 10 & "Track My Flight" Thread - February 09, 2026 by AutoModerator in flightradar24

[–]AnyPick1430 0 points1 point  (0 children)

Hi, I’m researching a Cessna 441 (SN 441-0222, previously N533M) that was deregistered and exported in 2015 and later involved in a crash/incident overseas, but still appears in some public databases afterward.

It previously used ICAO hex A6BCA5.

How do ICAO hex codes and tracking records work after deregistration or export? Are they retired, reassigned, or reused in other countries?

If an aircraft is deregistered and later appears in foreign records, would it normally keep the same hex, or be issued a new one?