English is not my "first" language. And here is what I can say about it:
If you are "educated" in english from the beginning during your pilot training, then it's most of the time natural to stick with english even when you have problems. Your QRH is in english, the courses and the manuals too, and if you have to say "turning inbound to establish on Ils 31L", you won't find quickly the words in your mother tongue, even in emergency. So it's only a question of education. I've heard that Air France years ago asked Boeing to have the cockpit indications translated. All their books, courses and procedures were teached in french...
