More than nine planes and nine ships scoured the Indian Ocean for missing Flight MH370 on Wednesday. Still, no one has the slightest idea where the Malaysia Airlines jet is, and officials are growing pessimistic that the mystery will ever be solved.
Angus Houston, the head of a joint agency coordinating the multinational search effort out of Australia, said no time frame has been set for the search to end, but that a new approach would be needed if nothing showed up.
"Over time, if we don't find anything on the surface, we're going to have to think about what we do next, because clearly it's vitally important for the families, it's vitally important for the governments involved that we find this airplane," he told Australian Broadcasting Corp. radio.
The Australian Maritime Safety Authority has stopped giving details of objects found in the sea.
Police are investigating the pilots and crew for any evidence suggesting they may have hijacked or sabotaged the plane. The backgrounds of the passengers, two-thirds of whom were Chinese, have been checked by local and international investigators and nothing suspicious has been found.
"Investigations may go on and on and on. We have to clear every little thing," Inspector General Khalid Abu Bakar told reporters. "At the end of the investigations, we may not even know the real cause. We may not even know the reason for this incident."
Police are also investigating the cargo and the food served on the plane to eliminate possible poisoning of passengers and crew, he said.
The British government said a nuclear-powered submarine with advanced underwater search capability had arrived in the southern Indian Ocean.
The current search area is a 85,000-square-mile patch of sea roughly a 2 1/2-hour flight from Perth. The focus of the search has moved several times as experts try to estimate where the plane is most likely to have landed based on assumptions on its altitude, speed and fuel. Currents in the sea are also being studied to see where any wreckage is most likely to have drifted.
Malaysia has been criticized by the relatives of some Chinese passengers on board, who accuse them of not giving them enough information or even lying about what it knows about the final movements of the plane. Some are staying in hotels in Beijing and Kuala Lumpur, courtesy of Malaysia Airlines.
On Wednesday, authorities organized a closed-door briefing in Malaysia for the families with officials and experts involved in the hunt, including the chief of the Malaysian air force.
It was relayed by video conferencing technologies to the relatives in Beijing. Malaysia's civil aviation chief, Azharuddin Abdul Rahman, said officials answered all the questions raised by the relatives and that they had "a very good meeting." Several relatives interviewed after the session said officials showed them more satellite and other data, but that they were still not satisfied.
"The fact is they didn't give us any convincing information," said Steve Wang, a representative of some of the Chinese families in Beijing. "They said themselves that there are many different possibilities, but they are judging on the basis of just one of them."
Malaysian officials have on occasion given conflicting accounts and contradictory information over the last three weeks. They maintain they are doing their best in what it is an unprecedented situation, and stress they want the same thing as the families, namely to locate the plane as quickly as possible.
A volunteer prepares for an event to remember the victims of the ill-fated flight MH370 on March 30, 2014 in Kuala Lumpur, Malaysia. (Rahman Roslan/Getty Images)