Indonesian navy divers took advantage of calmer waters on Monday to resume efforts to identify suspected wreckage from a missing Indonesia AirAsia passenger jet with no signal detected yet from the black box recorders.

Ships and aircraft seeking debris and bodies from the Airbus A320-200 widened their search area to allow for currents eight days after Flight QZ8501 plunged into the water en route from Indonesia's second-biggest city Surabaya to Singapore with 162 people on board. Helicopters will search coastal areas.

Indonesia's meteorological agency has said seasonal tropical storms probably contributed to the Jan. 28 crash and the weather has persistently hampered efforts to recover bodies and find the cockpit voice and flight data recorders that should explain why the plane crashed into the sea.

The main focus of the search is about 90 nautical miles off the coast of Borneo island, where five large objects believed to be parts of the plane - the largest about 18 metres (59 feet) long - have been pinpointed in shallow waters by ships using sonar.

Both flight recorders are located near the tail of the Airbus, but it was unclear whether that part of the aircraft was among the debris found on the seabed.

"The weather is quite conducive. The visibility is six kilometres, there's no low cloud, the wind is calm," Air Force Lt Col Jhonson Supriadi said.

"With our calculations of currents this strong, every day this operational area is extended."

Peter Marosszeky, a senior aviation research fellow at the University of New South Wales in Sydney, said the weather was squarely to blame for the delay in finding the black box recorders, which are designed to emit pings that can be detected by sonar for a month after a crash.

"The seas haven't been very friendly, but the black boxes have a 30-day life and they will be able to find them, particularly in the shallow waters," he said. "It's the weather that is causing the delay."

Nine ships from four countries have converged on the area, with teams of divers including seven Russian experts standing ready, but strong winds and four-metre high waves have kept progress agonisingly slow.

Thirty-four bodies of the mostly Indonesian passengers and crew have so far been recovered, including some still strapped in their seats. Many more may be still trapped in the body of the aircraft.

The crash was the first fatal accident suffered by the AirAsia budget group, whose Indonesian affiliate flies from at least 15 destinations across the sprawling archipelago.

The airline, which is 49 percent owned by Malaysia-based budget carrier AirAsia, has come under pressure from Indonesian authorities, who have suspended its Surabaya toSingapore operations saying the carrier only had a licence to fly the route on Mondays, Tuesdays, Thursdays and Saturdays.

Indonesia AirAsia said it would co-operate with the transport ministry while it investigates the licence.

A joint statement from Singapore's civil aviation authority (CAAS) and Changi Airport Group said that AirAsia had the necessary approvals to operate a daily flight betweenSurabaya and Singapore.