How does the aviation industry (pilots and ATC in particular, as opposed to cabin crew) train and certify English proficiency? Do they use classes and examinations associated with general-purpose English training, or ones specifically associated with the aviation industry?

I heard several years ago from Air Crash Investigation that a contributing factor for the [Avianca Flight 52](http://en.wikipedia.org/wiki/Avianca_Flight_52) crash was the use of the wrong terminology in communication between the non-native speaking pilots and the ATC.