Prince Charles is attributed to have said:

"The world's common language is bad english."

It is also true in flying. ATC in France is in French with French airliners, and accented english with the rest of us. Otherwise, 99% of the rest of the world uses english as the sole aviation language. Come to think of it, I think I heard a Japanese controller speaking Japanese to a JSDF F-15J once.

I would think a second language shows ability to learn, but doesn't have much to do with getting hired overall as a pilot, unless applying to an airline in a country such as those above.