Bad weather has hampered the search, keeping divers from looking for the wreck of the Airbus A320-200, which went down on Sunday en route from Indonesia's second-biggest city Surabaya to Singapore with 162 people on board.
The Indonesian-led search for the wreck of Flight QZ8501 is centred in the northern Java Sea, close to the Karimata Strait, where 10 bodies and pieces of the broken-up plane have been recovered. No survivors have been found.
"With the increasing amount of evidence and data, it's very likely we're getting closer to the fuselage of the AirAsia aircraft, based on what has been detected by sea vessels," Supriadi, operations director of the Indonesian search and rescue agency, told reporters.
Previous reports of a sonar image showing the plane body in the water have not been confirmed, officials said.
Two ships carrying hydrophones, or underwater listening devices, left the southern Borneo port of Pangkalan Bun on Friday, Indonesian officials said.
Aboard one vessel were experts from France's BEA accident investigation agency, which attends the crashes of all Airbus planes, although officials were unsure if the weather would allow the sensitive hydrophones to be deployed.
Search and rescue official Supriadi, who like many Indonesians uses just one name, said it was raining at the suspected crash site on Friday morning, with waves 3-4 metres (10-13 feet) high and wind speeds of 30-40 knots.
The cause of the crash - the first suffered by the AirAsia group since the budget operator began flying in 2002 - is so far unexplained. Investigators are working on a theory that the plane stalled as it climbed steeply to avoid a storm about 40 minutes into a flight that should have lasted two hours.
Officials earlier said it may take up to a week to find the black boxes, which investigators hope will unravel the sequence of events in the cockpit during the doomed jet's final minutes.
Even in bad weather, however, the search for the AirAsia plane is far less technically challenging than the two-year search for an Air France jet that crashed into deep Atlantic waters in 2009, or the so far fruitless hunt for Malaysia Airlines Flight MH370 that disappeared last year.
Given Flight QZ8501 crashed in shallow seas, experts say finding the boxes should not be difficult if its locator beacons, with a range of 2,000 to 3,000 metres (6,560 to 9,800 ft) and a battery life of around 30 days, are working.
So far, 10 bodies have been recovered from waters near the suspected crash site, search and rescue agency head Soelistyo said, along with debris such as a suitcase, an emergency slide and a life jacket.
The bodies are being taken in numbered coffins to Surabaya, where relatives of the victims, most of whom were Indonesian, have gathered. Authorities have been collecting DNA from relatives to help identify the bodies.
Relatives, many of whom collapsed in grief when they saw the first television pictures of the plane debris on Tuesday, held prayer vigils at Surabaya airport.
"UNBELIEVABLY" STEEP CLIMB
The plane was travelling at 32,000 ft (9,753 metres) and had asked to climb to 38,000 ft to avoid bad weather just before contact was lost. When air traffic controllers granted permission to fly at 34,000 ft a few minutes later, they received no response.
A source close to the investigation said radar data appeared to show the aircraft made an "unbelievably" steep climb before it crashed, possibly pushing it beyond the A320's limits.
"It appears to be beyond the performance envelope of the aircraft," he said.
The source, who declined to be identified, said 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.
The Indonesian captain, a former air force fighter pilot, had 6,100 flying hours on the A320 and the plane last underwent maintenance in mid-November, according to Indonesia AirAsia, which is 49 percent owned by Malaysia-based 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 disappeared 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.