Search teams looking for the sunken wreck of an AirAsia jet off Borneo struggled to resume full-scale operations on Thursday after a small window of fine weather closed, giving way to rising seas which have dogged the search from the start.
As dawn broke, revealing blue skies, hopes had risen for divers to be able to investigate what is believed to be the fuselage of the Airbus A320-200, which was carrying 162 people when it crashed on Sunday during stormy weather on a flight from the Indonesian city of Surabaya to Singapore.
"Clouds have started to descend again...and the weather conditions will deteriorate again," search and rescue official Tatang Zaenudin told TV, adding that the conditions would limit air searches. "For the sea search, we will continue."
A team of 47 Indonesian Navy divers is on standby to go down to a large, dark object detected by sonar on the ocean floor, lying just 30-50 metres (100-165 feet) deep. If it is the AirAsia plane, divers would look to retrieve its black boxes.
None of the tell-tale black box "pings" had been detected, an official said.
Investigators are working on a theory that the plane went into an aerodynamic stall as it climbed steeply to avoid a storm about 40 minutes into the flight.
So far, at least seven bodies have been recovered from waters near the suspected crash site, along with debris such a suitcase, an emergency slide and a life jacket.
The bodies are being taken in numbered coffins to Surabaya, where relatives of the victims have gathered, for identification. Authorities have been collecting DNA from the relatives to help identify the bodies.
Most of the 162 people on board were Indonesians. No survivors have been found.
Relatives, many of whom collapsed in grief when they saw the first grim television pictures confirming their fears on Tuesday, held prayers at a crisis centre at Surabaya airport.
'Unbelievably' steep climb
The plane was travelling at 32,000 feet (9,753 metres) and had asked to fly at 38,000 feet to avoid bad weather. When air traffic controllers granted permission for a rise to 34,000 feet a few minutes later, they received no response.
A source close to the probe into what happened said radar data appeared to show that the aircraft made an "unbelievably" steep climb before it crashed, possibly pushing it beyond the Airbus A320's limits.
"So far, the numbers taken by the radar are unbelievably high. This rate of climb is very high, too high. It appears to be beyond the performance envelope of the aircraft," he said.
The source, who declined to be named, added that more information was needed to come to a firm conclusion.
Online discussion among pilots has centred on unconfirmed secondary radar data from Malaysia that suggested the aircraft was climbing at a speed of 353 knots, about 100 knots too slow, and that it might have stalled.
Some of the bodies recovered so far have been fully clothed, including a flight attendant in her uniform. That could indicate the Airbus was intact when it hit the water and also support the aerodynamic stall theory.
The Indonesian captain, a former air force fighter pilot, had 6,100 flying hours under his belt and the plane last underwent maintenance in mid-November, according to the airline, which is 49 percent owned by Malaysia-based budget carrier AirAsia.
Three airline disasters involving Malaysian-affiliated carriers in less than a year have dented confidence in the country's aviation industry and spooked travellers.
Malaysia Airlines Flight MH370 went missing in March en route from Kuala Lumpur to Beijing with 239 passengers and crew and has not been found. On July 17, the same airline's Flight MH17 was shot down over Ukraine, killing all 298 people on board.
On board Flight QZ8501 were 155 Indonesians, three South Koreans, and one person each from Singapore, Malaysia and Britain. The co-pilot was French.
The AirAsia group, including affiliates in Thailand, the Philippines and India, had not suffered a crash since its Malaysian budget operations began in 2002.