WELLINGTON, New Zealand (AP) — The plane must be somewhere. But the same can be said for Amelia Earhart's.

Ten days after Malaysia Airlines Flight 370 disappeared with 239 people aboard, an exhaustive international search has produced no sign of the Boeing 777, raising an unsettling question: What if the airplane is never found?

Such an outcome, while considered unlikely by many experts, would certainly torment the families of those missing. It would also flummox the airline industry, which will struggle to learn lessons from the incident if it doesn't know what happened.

While rare nowadays, history is not short of such mysteries — from the most famous of all, American aviator Earhart, to planes and ships disappearing in the so-called Bermuda Triangle....