[myblake]

On the one hand, totally reasonable to ask “what does speaking English have to do with building airplanes”.

On the other, the vast majority of technical and scientific literature worldwide is English language based. As is all air traffic control. So, reasonable chance the maintenance manuals are in English.

That said I am with you on disliking the implicit xenophobia in the question.

[pinkmuffinere]

+1 to this. It would be more work to write the manuals in multiple languages, and there could be slight differences in making, Nonetheless, I bet this would be worthwhile. Or maybe there is a language better than English for the manuals.