Two U.S. Navy Aircraft Join Hunt for Missing Jet

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Two U.S. Navy aircraft joined the hunt for the missing Malaysia Airlines jet on Sunday.

The P-3 Orion and a MH-60R helicopter were searching over international waters around the last known positions of the Boeing 777, which vanished carrying 239 people.

"No one is sure of exactly where to look or even what there is to find," a Navy official told NBC News.