This topic will be interesting.
As of my research, the following countries may use their local languages on ATC:
·France
·China(Mandarin, excluding region of Hong Kong FIR, Macao Airport and Taiwan Province)
·Spain
·Latin American Spanish-speaking countries
·Russia
·the CIS(Belarus, Azerbaijan, etc.)
·Germany (mentioned by @drqt3375 )
·Sweden (mentioned by @drqt3375 )
·Finland (mentioned by @drqt3375 )
(May be other countries/regions not listed)
Also, each of these countries may also have their ATC Standards on their own languages.
Ohter than these countries, ATC are all in English, but in some cases, local languages are allowed. For example, Japan use English on ATC, but if in emergency, and if both controller and pilot are Japanese native, they are allowed to use Japanese to avoid misunderstanding.
Also in China, if it is the case listed below, ATC uses English as well.
-If the pilot for communication is not Chinese-Native (no matter it is a foreign airliner or a Chinese airliner flying by foreign pilots, or maybe the one who is not lisenced for Chinese Mandarin ATC)
-If the flight procedure require English ATC communication or even full English procedure(the example is flying A380 by China Southern even if the pilots are all Chinese, or sometimes Hainan Airlines may have this request)
-If is in Air Control Region of Hong Kong FIR (including VMMC Macao Airport) or in Taiwan Province (they speak English on ATC by standards but as I know, Taiwan pilots are optional allowed to speak Mandarin when flying in Mainland area).
By the way, it might be off topic, but even if they are English, the English ATC in USA and out of USA are different. Currently, the game ATC is based on USA (FAA Regulation), but most of the world uses ICAO Regulation based ATC communication.
My recommendation is:
- When Real ATC comm applied, only allow France, China, Spain etc. to use local language in their countries on ATC. Other countries/regions use English.
- Add a setting in aircraft ATC configuration (together with call sign, tail number) to allow user to force using English on ATC.
References I’ve found: