In accordance with the rules of the International Civil Aviation Organization ICAO, “pilots, air traffic controllers and operators of air navigation stations participating in international operations must speak English at a level of at least 4 on the ICAO language proficiency scale».
But what about pilots who fly only domestically, or those who fly only general aviation aircraft?
In general, are there any rules for using English when communicating with ATC?
Legal — No. And even the rules do not always require the use of English. According to ICAO Annex 10, “air-to-ground radiotelephony” must be in the language normally used by the ground station, or in English.
Thus, there are no rules forbidding the German crew flying to Frankfurt from speaking German. But even then, the radio is likely to be in English, especially at such a large airport.
When approaching for a landing, gathering information from the aircraft in front can be critical. It is possible that the weather suddenly changed just a few kilometers from the runway, and the predicted safe landing conditions no longer exist. If pilots have this information at an early stage, they will have more opportunities to make a decision: go around and wait for the storm to end, or immediately look for an alternate airport. But if there is a language barrier, and the controller does not repeat the new information in English, the pilots will have to deal with the changed conditions themselves. And do it in a state of time pressure. Therefore, as a safety standard, the largest airports in the world operate in English.
But because the rules are flexible, European controllers and pilots still address each other in French or German. And on flights in China and Taiwan, Chinese is used.
Smaller airports that don't handle international flights other than private jets can afford to be more casual about the language. Dispatchers may only have a limited command of English as they do not use it as often. In general, when you're primarily concerned with the safety of local business jets, it's probably easier to use language that most radio listeners can understand.
History knows cases where language has been a negative factor in notable incidents .
It was recently the anniversary of the Tenerife tragedy, which involved KLM and Pan Am flights. Not only did critical radio interference “help” to the KLM crew to miss ATC instructions, and several misunderstandings arose between all parties. In the section “Probable Causes” there is a clause about “ambiguous radio communications in English.” Later, aviation regulators introduced new, clearer rules regarding certain words and expressions.
There was also an American Airlines passenger flight flying from Miami to Colombia. On December 20, 1995, a Boeing 757–200 crashed into a mountain. Loss of situational awareness and refusal to abort approach to Cali in adverse conditions were cited as the main reasons, the difficulty of the American crew in communicating with the Colombian air traffic controllers played an evil role.