Malaysian authorities say they are not sure which direction missing jet was headed

KUALA LUMPUR, Malaysia – More than four days after a Malaysian jetliner went missing en route to Beijing, authorities acknowledged Wednesday they didn't know which direction the plane carrying 239 passengers was heading when it disappeared, vastly complicating efforts to find it.

Amid intensifying confusion and occasionally contradictory statements, the country's civil aviation authorities and the military both said the plane may have turned back from its last known position between Malaysian and Vietnam, possibly as far as the Strait of Malacca, a busy shipping lane on the western side of Malaysia.

How it might have done this without being clearly detected remains a mystery, raising questions over whether its electrical systems, including transponders allowing it to be spotted by radar, were either knocked out or turned off. If it did manage to fly on, it would challenge earlier theories that the plane may have suffered a catastrophic incident, initially thought reasonable because it didn't send out any distress signals.

Authorities have not ruled out any possible cause, including mechanical failure, pilot error, sabotage or terrorism in the disappearance of the plane. Both the Boeing 777 and Malaysia Airlines have excellent safety records. Until wreckage or debris is found and examined, it will be very hard say with any level of certainty what happened.

The search for the missing aircraft was begun from the spot it was last reported to be over the ocean between Malaysia and Vietnam. But they have also said search operations were ongoing in the Strait of Malacca. Scores of planes and aircraft have been scouring waters in both locations.

The country's air force chief, Gen. Rodzali Daud, released a statement denying remarks attributed to him in a local media report saying that military radar had managed to track the aircraft turning back from its original course, crossing the country and making it to the Malacca strait to the west of Malaysia. The Associated Press contacted a high-level military official, who confirmed the remarks.

Rodzali referred to a statement he said he made March 9 in which he said the air force has "not ruled out the possibility of an air turn back" and said search and rescue efforts had been expanded to the waters around Penang Island, in the northern section of the strait.

It is possible that the radar readings are not definitive or subject to interpretation, especially if a plane is malfunctioning.

"There is a possibility of an air turn back. We are still investigating and looking at the radar readings," the country's civilian aviation chief Azharuddin Abdul Rahman said Wednesday.

The Strait of Malacca that separates Malaysia from Indonesia's Sumatra Island is some 400 kilometers (250 miles) from where the plane was last known to have made contact with ground control officials over the Gulf of Thailand at a height of 35,000 feet (almost 11,000 meters) early Saturday.

Adding to the confusion, Indonesia air force Col. Umar Fathur said the country had received official information from Malaysian authorities that the plane was above the South China Sea, about 10 nautical miles from Kota Bharu, Malaysia, when it turned back toward the strait and then disappeared. That would place its last confirmed position closer to Malaysia than has previously been publicly disclosed.

Fathur said Malaysian authorities have determined four blocks to be searched in the strait, which Indonesia was assisting in.

Vietnam continued to search for the plane on land and sea. In its area of responsibility, some 22 aircraft and 31 ships from several countries were involved, according to Lt. Gen. Vo Van Tuan, deputy chief of staff of Vietnamese People's Army.

Malaysian police chief Khalid Abu Bakar, who has been ordered to look at possible criminal aspects in the disappearance of the plane, said hijacking, sabotage and issues related to the pilots' psychological health were being considered.

An Australian TV station reported that the first officer on the missing plane, Fariq Abdul Hamid, had invited two women into the cockpit during a flight two years ago. One of the women, Jonti Roos, described the encounter on Australia's "A Current Affair."

Roos said she and a friend were allowed to stay in the cockpit during the entire one-hour flight on Dec. 14, 2011, from Phuket, Thailand, to Kuala Lumpur. She said the arrangement did not seem unusual to the plane's crew.

"Throughout the entire flight, they were talking to us and they were actually smoking throughout the flight," said Roos, who didn't immediately reply to a message sent to her via Facebook. The second pilot on the 2011 flight was not identified

Malaysia Airlines said they took the allegations seriously.