More nations have joined the effort to locate the missing Indonesia AirAsia jet, which a senior Indonesian official said might have ended up in the bottom of the sea.
After a full day's operations, which threw up its share of false hopes and illusory clues, search teams made little headway in locating the plane or its wreckage.
Basarnas, Indonesia's search and rescue agency, also appeared to confirm what many had already feared.
Mr Bambang Soelistyo, head of Basarnas, told reporters that based on its coordinates, the plane may have ended in the sea. "So for now, we think it is on the sea floor," said Mr Soelistyo.
Singapore is sending two teams of specialists and two sets of underwater locator beacon detectors to look for the plane's black boxes. South Korea became the latest nation to participate in the search, sending a P3 Orion to join planes and ships from Singapore, Malaysia and Australia.
Flight QZ8501 flying from Surabaya to Singapore with 162 on board, including a Singaporean infant, disappeared in bad weather minutes after seeking permission to climb higher to avoid monsoon-heavy clouds.
There was no distress signal and other aircraft present in the area did not spot the plane, which is said to have been carrying fuel to fly another four hours.
Two of Singapore's C-130 military planes have been scouring the area while the frigate RSS Supreme and missile corvette RSS Valour had commenced sea searches. A Singapore landing ship tank is also on its way and will be followed by the MV Swift, a submarine support and rescue vessel.
India and China also offered help to locate the plane, whose loss caps a miserable year for South-east Asian aviation coming in the wake of two Boeing 777 aircraft lost by Malaysia Airlines.
Indonesian President Joko Widodo told a media briefing: "We have to be frank that up to now there is not yet any indication as to where the plane is."
Vice-President Jusuf Kalla called for calm and vowed to find the AirAsia plane.
"This is the biggest search operation that we have ever done," he said. "Searching at sea is not as easy as searching on land. But we have faced similar difficulty in the past during the Adam Air crash and with God's help we finally found it."
In 2007, an Adam Air Boeing 737 went down off Sulawesi with 102 on board. It took more than a week to locate the plane and several months to recover the flight data recorders. This time, Indonesia has accepted offers of help from Britain, the United States and France for underwater equipment to locate the black boxes.
For a brief while yesterday, hope flickered that the wreckage of the plane may have been spotted after an Indonesian Air Force C-130 reported sighting a vast oil spill that, some suspected, could have come from the doomed plane.
A vessel was dispatched to the area, only to reveal that the suspected oil slick was, in fact, a range of reefs, said Mr Soelistyo.
He also told The Straits Times: "We also just received reports of a fisherman hearing a loud bang and another fisherman seeing a plane flying low south of Pangkalanbun (West Kalimantan). We are sending out a team to check this."
The authorities in Jakarta said they would investigate the airline to see if it had upheld proper standards. Indonesia AirAsia is 49 per cent owned by Malaysia's AirAsia Group, led by feisty entrepreneur Tony Fernandes. The parent company's stock fell sharply yesterday on the bad news.
Mr Fernandes said on Twitter: "Keeping positive and staying strong. My heart bleeds for all the relatives of my crew and our passengers. Nothing is more important to us."
This article was first published on Dec 30, 2014. Get a copy of The Straits Times or go to straitstimes.com for more stories.