It's not related to Chinese in specific, but in civilian air traffic, the lingua franca is specifically English[0]. The reason for this is because other languages leave too much room for interpretation. One incident not mentioned in that page that's worth bringing up is Korean Air Flight 801; the crew recognized an issue with the instruments quite a bit before the crash, but because the flight crew essentially was too polite in notifying the captain of the issue, the captain instead asserted authority with incomplete information, leading to the plane crashing[1].
Language specificity and cultural encoding in those languages can have a pretty major impact on its clarity, especially in critical situation. Speaking a secondary language instead can avoid that sort of thing simply because being a non-native speaker, you'll be a good deal more blunt in that language.