Flaw in technology.
200+ years in our future and they don't have body modification personal computing devices installed allowing translation of any language to English and back? At least the Flight crew would have subcutaneous cybernetics especially engineers, navigators and pilots. There's no reason why he couldn't have his personal cyber assistant translate the other crew member's Vietnamese. Facebook does it now, and fairly reliably, for Thai or Vietnamese. In 200 years a simple smart phone-like device, injected on the temple, could probably draw it's power from human movement.