That's not true, you can use the local language as well. What is required is to answer in English if prompted in English. Though nowadays most major airports p

That's not true, you can use the local language as well. What is required is to answer in English if prompted in English. Though nowadays most major airports probably are English only, it wasn't so long ago that pilots were complaining that most of the traffic at CDG was in French for instance. For what it's worth, I believe Japan is very strict in the English only however.