Teams searching for the wide-body jetliner that vanished off Vietnam almost certainly will locate it and figure out what brought it down, according to aviation investigators and case files spanning four decades.

Planes seemingly lost without a trace in waters miles deep have been found by remote-controlled submarines, or investigators gathered enough clues to determine what happened, according to accident reports since 1970.

“I think they'll find it,” Ronald Schleede, a former investigator with the U.S. National Transportation Safety Board, said in an interview about Malaysia Airlines Flight 370. “The capability is there. Someone just has to put the money up.”


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The Malaysian Boeing 777-200, carrying 239 people, never reported in with Vietnam's air-traffic controllers after leaving Malaysian airspace and flying across the Gulf of Thailand toward Beijing on March 8.

A suspected fragment from the plane, either a window or emergency door, was spotted by helicopter 56 miles south of Vietnam's To Chu Island, Le Van Minh, a Vietnamese coast guard commander, said in a telephone interview Monday. Rough seas and darkness were preventing crews from retrieving it.

An air search also found what appeared to be two fuel slicks as long as 15 kilometers off Vietnam's south coast.

Waters in the Gulf of Thailand rarely get more than 164 feet deep and the bottom tends to be flat, said John Fish, vice president of American Underwater Search and Survey of Bourne, Mass., in an interview. So the plane will be relatively easy to locate and recover if it went down there, Fish said.

Fish has been involved in recovery efforts on accidents including the 1996 crash of Trans World Airlines Flight 800 off New York.

Black-box recorders, which are hardened to withstand a crash, emit a pinging sound for at least 30 days after being submerged, which will help crews locate them, he said.

Even if the pingers can't be traced, current underwater technology, which can map the ocean floor with high-definition sonar, operates at the deepest depths known, he said.

A team led by Woods Hole Oceanographic Institution in Massachusetts located the wreckage of Air France Flight 447, which went down June 1, 2009, in the Atlantic Ocean off the coast of Brazil, after a search that took almost two years. The plane came to rest at a depth of more than 2 miles, in an area of steep undersea mountains, and ships couldn't trace the pingers.

“That's improved so much over the past few years,” Thomas Haueter, former chief aviation investigator at the NTSB, said in an interview. “What the French did was really incredible. You take a look at the depth of the water.”

Schleede, Haueter and John Cox, an accident investigator and chief executive officer at Safety Operating Systems in Washington, said they weren't aware of any over-water crashes since the 1970s that weren't solved.

In the handful of cases in which the black-box data or voice recorders weren't recovered or stopped functioning, which can happen in cases of mid-air breakups or explosions, investigators obtained enough information from other sources to get an idea of what occurred, they said.

The recorders weren't found on an Asiana Airlines Inc. 747 freighter that went down in the East China Sea on July 28, 2011, Haueter said. The pilots, both of whom died, reported a fire aboard the plane before it disappeared.

Investigators analyzed wreckage pulled from the ocean floor to determine that a bomb in the forward cargo hold brought down an Air India Boeing 747 off the coast of Ireland in 1985, killing 329 people, according to the agency then known as the Canadian Aviation Safety Board. It was the deadliest act of terrorism involving an airliner until the Sept. 11, 2001, attacks.

Following the crash of a Taiwan China Airlines 747 into the Taiwan Strait on May 25, 2002, investigators found from the wreckage that a repair on the plane's tail failed, causing it to break apart, according to the Taiwan Aviation Safety Council. All 225 people aboard the Taipei-to-Hong Kong flight died.

Once the missing Malaysian plane is found, recordings from the flight deck and the plane's instruments, along with physical clues, will help shed light on what caused it to go down, whether it was terrorism, errors by the pilots, a mechanical failure or some other issue, the investigation experts said.

“I believe very strongly that they will find the airplane, they will get the recorders and we will learn definitively what happened to this Boeing 777,” Cox said.