My own interpolation of the legalities of this are as follows (and I stand to be corrected)
The five ICAO languages, English, French, Spanish, Arabic and Russian are only designated by the Convention for presentation of ICAO documentation to members and this designation does not extend to operational use, RT etc.
ICAO Annex 6 'Operation of Aircraft' makes no statement that I can find, directly or indirectly, as to the language to be used for RT etc. (it only covers validity of licenses, communication equipment required etc.). I do not have ICAO PANS OPS. readily available to clarify any requirement at the Controller end.
The adoption of English as the International Language in the air has very vague roots in the now dated provisions of the International Telecommunications Union which designates English as the spoken language to be used to communicate 'with a vessel on the high seas i.e. international waters'. There is no parallel ICAO legislation/guidance.
Now what can clearly be seen is a large and potentially dangerous 'black hole' of no ICAO legislation covering the language to be used between ATC and Aircraft...there isn't any!
Last edited by Boss Raptor; 4th Aug 2003 at 16:20.