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 original route toward Vietnam, possibly as far as the Strait of Malacca on the eastern side of the country.
How it might have done this without being clearly detected remained a mystery, raising questions over whether its electrical systems were either knocked out or turned off.
Authorities have not ruled out any possible cause, including mechanical failure, pilot error, sabotage or terrorism in the disappearance of the plane. The 777 is a modern aircraft with an excellent safety record, as does Malaysia Airlines.
Authorities began their search for the missing aircraft at the position it was last reported to be at over the sea between Malaysia and Vietnam. But they have also said search operations were ongoing in the Malacca strait. Scores of planes and aircraft have been scouring 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.
The country's civilian aviation chief Azharuddin Abdul Rahman said he could neither confirm nor deny military's remarks. That suggests disagreement or confusion at the highest level over where the plane is most likely to have ended up.
"There is a possibility of an air turn back. We are still investigating and looking at the radar readings," he said Wednesday
The strait is a busy shipping lane that separates Malaysian from Indonesia's Sumatra Island.
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 Malaysia authorities have determined four blocks to be searched in the strait, which Indonesia was assisting in.
Vietnamese military authorities said they were searching for the plane on land sea.
Lt. Gen. Vo Van Tuan, deputy chief of staff of Vietnamese People's Army, said there were 22 aircraft and 31 ships from Vietnam and other countries involved in the hunt in its area of responsibility.
Flight MH370 took off from Kuala Lumpur at 12:41 a.m. Saturday, bound for Beijing. Authorities initially said its last contact with ground controllers was less than an hour into the flight at a height of 35,000 feet, when the plane was somewhere between the east coast of Malaysia and southern Vietnam.
Malaysian police chief Khalid Abu Bakar, who has been ordered to look at possible criminal aspects in the disappearance of Flight MH370, 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.