> this is an issue in, for example, Spain where the radio communication is often in Spanish and many pilots flying there don't understand Spanish
How does that happen? I was under the impression that all flight communication was supposed to be performed in English, even in countries where English is not very commonly spoken (e.g. Spain).
Many countries allow "English or the local language". Well-known examples are China, France, Russia, Spain, Germany. I've also heard it in Italy and the Netherlands.
The extent of use of local language varies - in NL I've mostly only heard it for a small amount of non-formal conversation, maybe a Dutch word at the end of a transmission. In Spain it's extremely common for entire transmissions to be in Spanish.
Obviously this is only done when both the transmitter and the receiver of the transmission understand the local language. It is (in my opinion and many other people's) a safety issue because it reduces the situational awareness of everyone else on frequency.
How does that happen? I was under the impression that all flight communication was supposed to be performed in English, even in countries where English is not very commonly spoken (e.g. Spain).