@nuname
You're missing the point completely.
If you require people to use one language on the radio for international flights, that does not stop there from being two or more languages on the radio, because not all flights are international.
You have no right to tell a person of country X that they have to learn a different language so they can fly even if they never leave their own country.
This would be the same as saying that in order to get a drivers license in the USA, you have to learn to speak Chinese.