By Simon Denyer, William Wan and Ashley Halsey III

The Washington Post

BEIJING — Frustration mounted Monday over what has become one of the most perplexing aviation disasters in history, as the search for a vanished Malaysia Airlines passenger jet dramatically expanded in its third day.

Hopes for a breakthrough were dashed when Malaysian authorities said oil found on the ocean surface had been tested and found not to have come from the jetliner. Various pieces of flotsam picked up in the vicinity of the plane’s last known location were also found to be unconnected.

“This unprecedented missing aircraft mystery — as you can put it — it is mystifying,” Azharuddin Abdul Rahman, director general of Malaysia’s Department of Civil Aviation, said at a news conference in Kuala Lumpur.

“To confirm what happened that day on this ill-fated aircraft, we need hard evidence,” he said. “We need concrete evidence. We need parts of the aircraft for us to analyze, for us to do forensic studies.” He added, “We are every hour, every minute, every second, looking at every inch of the sea.”

About 40 ships and 34 aircraft from nine countries are combing a vast area of ocean in the Gulf of Thailand and the South China Sea, northeast of Malaysia toward Vietnam. The search expanded Sunday into areas well beyond the plane’s intended northeasterly flight path toward China. Authorities are now looking even at areas in the Andaman Sea, on the western side of the Malaysian peninsula.

For the plane to have crashed into the Andaman Sea would imply that it had somehow turned back and crossed the entire Malaysian peninsula without being detected by radar operators.

Malaysian authorities said Sunday that the plane may have turned around before disappearing from radar without a distress call. If true, aviation experts said this could offer a clue as to why no debris had yet been found.

“Was this turn under pilot command, hijacker command, or induced by a structural failure of some kind — either by an airplane fault or by a bomb?” wrote Scott Hamilton, an aviation expert and founder of Leeham News and Comment, in an email from Seattle.

“If the airplane deviated from its planned flight path (as a turn might indicate), they are looking in the wrong place. Also, the fact that no debris whatsoever has emerged from where they are looking, this certainly suggests to me they are looking in the wrong place, whatever the reason.”

In a vacuum of hard evidence about what went wrong aboard the flight, speculation turned to the possibility of pilot suicide, an extraordinarily rare occurrence that has taken down two commercial airliners in recent years.

“You have to ask the question,” said one U.S. aviation official who was not authorized to discuss the matter publicly.

The Malaysia Airlines flight reportedly was being tracked by radar when its transponder went dark. There were no radio transmissions to indicate that anything was amiss aboard the plane. Both the transponder signals and radio communication are controlled by the pilot.

“They need to be able to control the electronics from the cockpit in case there is a short-circuit,” the U.S. official said. “The pilot also can turn off the voice recorder.”

That’s what investigators believe happened aboard SilkAir Flight 185 before it spiraled to the ground in Indonesia in 1997, killing 97 passengers and seven crew members.

While Indonesian investigators said they could not determine what caused the crash, a team of U.S. investigators said someone in the cockpit — most likely the captain — turned off the transponder and cockpit recorder and took the plane into a fatal dive.

Asked how a pilot or co-pilot would let his colleague intentionally crash the plane, the U.S. official said: “It’s easy. You wait until the other guy leaves to use the bathroom. Even though he has a key (to the cockpit), you have time.”

Or, he said, there may have been a struggle between crew members that went unrecorded because the cockpit recorder had been turned off.

That’s what happened aboard the EgyptAir Flight 990, which has received renewed attention after the Malaysia Airlines flight went missing.

The 1999 Egyptian flight crashed into the Atlantic south of Nantucket, killing 217 people.

U.S. investigators concluded that the crash was caused by crew member Gameel Al-Batouti.

The cockpit recorder on that flight was activated, and it recorded the flight’s captain departing for the rest room. Thirty seconds later, Al-Batouti said in Arabic, “I rely on God.” The autopilot was disengaged and the plane began an erratic pattern that investigators said could not have been caused by a mechanical malfunction. When the captain rushed back to the cockpit to confront Al-Batouti, both engines had been shut down.

While the captain struggled to bring the plane’s nose up again, Al-Batouti was on his own set of controls, working to keep the plane in a dive.

The National Transportation Safety Board determined that the crash was “a result of the relief first officer’s flight control inputs. The reason for the relief first officer’s actions was not determined.”

In a phone interview Monday, a spokesman for the U.S. Navy’s 7th Fleet, Navy Cmdr. William Marks, confirmed that the USS Pinckney has joined the search. Marks told the BBC that the destroyer and the helicopters it carries have infrared, sonar and other search capabilities and can also listen for any signal emitted from the plane’s black box.

“Just from the air, we can see things as small as almost the size of your hand or a basketball. It’s not a matter of if we can see it. It’s an extremely large area,” he said. As more time passes, currents and wind as well as the expanding size of the search area are making the task more difficult.

On Monday, hopes briefly centered on a rectangular orange object that authorities said might have been a lifejacket. But when a Vietnamese helicopter recovered the piece of flotsam, it was identified as “a moss-covered cap of a cable reel,” the Civil Aviation Authority of Vietnam said on its website.

This was not the first time hopes have been dashed in the past two days.

Late Sunday afternoon, Vietnamese authorities said one of their aircraft had spotted a rectangular object that could have been an inner door from the missing plane, but it was too dark to be sure. By Monday, ships and planes had returned to the area, but could not locate the object. Meanwhile, sightings of what had resembled a piece of the plane’s tail turned out to be logs tied together to form a pontoon, Malaysian authorities said.