The mystery over the plane's whereabouts has been confounded by confusing and occasionally conflicting statements by Malaysian officials, adding to the anguish of relatives of the 239 people on board the flight - two thirds of them Chinese.
"There's too much information and confusion right now. It is very hard for us to decide whether a given piece of information is accurate," Chinese Foreign Ministry spokesman Qin Gang told reporters in Beijing. "We will not give it up as long as there's still a shred of hope."
The mother of passenger Zou Jingsheng, who would only give her name as Zou, wept and spoke haltingly about her missing son while staying at a hotel near the Beijing airport. She expressed frustration with the airline and the Malaysian government over their handling of the case.
"I want to talk more, but all this is very stressful, and after all it is my son's life that I am concerned about. I just want to know where he is, and wish he is safe and alive," she said.
Malaysia Airlines flight 370 took off from Kuala Lumpur for Beijing early Saturday morning and last made contact with ground control officials about 35,000 feet above the Gulf of Thailand between Malaysia and southern Vietnam before vanishing.
Dozens of planes and ships from at least eight nations are scouring waters on both sides of peninsular Malaysia but have found no trace of the jet.
Citing military radar, Malaysian authorities have said the plane may have turned back from its last known position, possibly making it as far as the Strait of Malacca, a busy shipping lane west of the narrow nation some 400 kilometers (250 miles) from the plane's last known coordinates.
How it might have done this without being clearly detected has raised questions over whether its electrical systems, including transponders allowing it to be identified 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. Both the Boeing 777 and Malaysia Airlines have excellent safety records. Until wreckage or debris is found and examined, it will be very hard to say what happened.
"There is a possibility that the aircraft, the flight, has taken a turn back basing on the radar we have used to pick up the signal," Malaysia's armed forces chief, Gen. Zulkifeli Mohammad Zin told The Associated Press. "We cannot confirm it, but, basing on that, even though there is a possibility there, we have got to conduct a search (in the strait). We cannot leave it to chance."
Finding wreckage from a missing plane can sometimes take days or longer, depending on the nature of the crash, the current and how much is known about the aircraft's final movements.
India's ministry of external affairs spokesman Syed Akbaruddin said Wednesday that Malaysian authorities had contacted their Indian counterparts seeking help in searching areas near the Andaman Sea.
Malaysia'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. 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 that search and rescue efforts had been expanded to the waters around Penang Island, in the northern section of the strait.
It's possible that the radar readings are not definitive or subject to interpretation, especially if a plane is malfunctioning.
Even so, the confusion has prompted speculation that different arms of the government have different opinions over where the plane is most likely to be, or even that authorities are holding back information.
Choi Tat Sang, a 74-year-old Malaysian man, said the family is still holding out hope that the plane and all on board are safe. His daughter in law, Goh Sock Lay, 45, is the chief stewardess on the flight. Her 14-year-old daughter, an only child, has been crying every day since the plane's disappearance.
"We are heartbroken. We are continuing to pray for her safety and for everyone on the flight," he said.
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 20 kilometers (12 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.