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The top priority for investigators trying to discover what happened to Malaysian Airlines Flight 370 will be locating and retrieving its wreckage, an expert said Saturday.

"It’s important to get as much of the wreckage back to the shore," analyst Chris Yates told NBC News. "Only then can you properly begin to investigate."

Earlier, the Vietnamese air force reportedly spotted two oil slicks consistent with fuel from a crashed jet off its coast.

When Air France Flight 447 went down in the Atlantic Ocean in June 2009, bodies and some parts of the plane were found within two weeks, but it took two years to locate the main wreckage.

Yates, a former aviation security editor at IHS Jane's, highlighted that the Boeing 777 has "an exemplary safety record."

He added: "It's been flying for 20 years and only suffered one fatal accident last year in San Francisco. We could be looking at mechanical failure, we could be looking at terrorism."

Duncan Golestani of NBC News contributed to this report.