For many countries, the registration number begins with a obvious letter (F for France, D for German (Deutschland I guess), C for Canada,...). For other, historical reasons have already been covered here (e.g. Where did the US 'N' registration letter come from?).

But for Belgium, I find it weird to begin with OO. Is there an historical reason for that? if so, what is it?

  • 3
    $\begingroup$ D is for Djermany. Just say it aloud and suddenly it makes sense. ;-) $\endgroup$
    – PerlDuck
    Commented Apr 18, 2020 at 8:14
  • $\begingroup$ And G for UK-registered aircraft (for some reason), EI for Ireland (Eire), RA for Russia, JA for Japan, I for Italy, UR for the Ukraine, CU for Cuba, YU for Serbia (formerly Yugoslavia), LX for Luxembourg, Z for Zimbabwe... $\endgroup$
    – Vikki
    Commented Apr 18, 2020 at 17:34

1 Answer 1


Since nearly all aircraft have radios, the simplest solution was to make aircraft tail numbers the same as their radio callsigns. Belgium was allocated radio callsigns with the prefixes ON through OT by the ITU, though for whatever reason, they use only prefix OO for aircraft.

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    $\begingroup$ Well, now the question becomes: why did they get such radio callsigns? $\endgroup$
    – Zeus
    Commented Apr 20, 2020 at 0:48
  • 1
    $\begingroup$ and what is this "whatever reason"? $\endgroup$
    – Manu H
    Commented Apr 20, 2020 at 9:21
  • $\begingroup$ @Zeus Good question, but I suspect not topical here since it's not specific to aviation. $\endgroup$
    – StephenS
    Commented Apr 20, 2020 at 20:07

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