A police investigation may never determine the reason why Malaysia Airlines Flight 370 disappeared, and search planes scouring the Indian Ocean for any sign of its wreckage aren't certain to find anything either, officials said Wednesday.
The assessment by Malaysian and Australian officials underscored the lack of knowledge authorities have about what happened on Flight 370. It also points to a scenario that becomes more likely with every passing day — that the fate of the plane and the 239 people on board might remain a mystery forever.
The plane disappeared March 8 on a flight to Beijing from Kuala Lumpur after its transponders, which make the plane visible to commercial radar, were shut off. Military radar picked up the jet just under an hour later, on the other side of the Malay peninsula. Authorities say that until then its "movements were consistent with deliberate action by someone on the plane," but have not ruled out anything, including mechanical error.
Police are focused on 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," Malaysian 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 search-and-rescue teams are in a race against time to locate the plane's black-box recorder, which has an expected battery life of around 30 days and without which it may never be possible to explain the plane's mysterious disappearance.
The search for the plane began over the Gulf of Thailand and South China Sea, where its last communications took place, and then shifted west to the Strait of Malacca, where it was last spotted by military radar.
Up to 10 planes and nine ships from a half dozen countries are scouring a stretch of the Indian Ocean roughly the size of Britain, where the plane is believed to have crashed more than three weeks ago.
Retired Air Chief Marshal Angus Houston, the head of the Australian agency coordinating the operation, said a lack of reliable flight telemetry and punishing conditions at sea were making the operation even more challenging.
"In other words, we don't have a precise aircraft location for six hours before the aircraft went into the water somewhere," he said in an interview with the Australian Broadcasting Corporation on Wednesday. "The reality is it's the most complex and challenging search-and-rescue operation, or search-and-recovery operation now, that I've ever seen."
With no other data available indicating where the plane went down, spotting wreckage is key to narrowing the search area and ultimately finding the flight data recorders, which will provide a wealth of information about the conditions the aircraft was flying under and possibly the communications or sounds in the cockpit.
Malaysia has been criticized by the relatives of some Chinese passengers on board, who accuse it of not giving them enough information or even lying about what it knows regarding 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 videoconferencing technologies to the relatives in Beijing.
Malaysia's civil aviation chief, Azharuddin Abdul Rahman, said officials had 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 is an unprecedented situation, and they stress they want the same thing as the families, namely to locate the plane as quickly as possible.
Malaysia on Tuesday released the full transcript of communications between the Boeing 777 and local air-traffic control before it dropped from civilian radar. The last words from the cockpit were a standard "Good night Malaysian three seven zero," Malaysian authorities said, changing their account of the critical last communication from a more casual "All right, good night."