DHAKA: Nearly two dozen ships and aircraft are picking up the search for Malaysia Airlines Flight 370 in fair weather Friday, seeking a breakthrough in the seas far off Australia.

The day`s search area has been refined to about 217,000 square kilometers (83,800 square miles) of a remote part of the Indian Ocean northwest of Perth, Australia`s Joint Agency Coordination Centre reported.

A total of 14 aircraft and nine ships will scan the area, and two ships seen as central to the hunt were expected to reach the zone soon.

But officials have warned of a potentially long search for the missing passenger jet, which vanished nearly four weeks ago with 239 people on board. Long days spent combing vast tracts of ocean have so far turned up no trace of the plane.

The Royal Navy survey ship HMS Echo will be conducting a specific search on Friday, a spokesperson for the Australian Defence Force told CNN. And the Australian naval supply ship Ocean Shield, which is equipped with U.S. technology designed to detect the pings from the flight recorders, was due to arrive in the search area overnight.

The spokesperson, who is not authorized to speak to the media, told CNN there would be a news conference on Friday led by retired Air Chief Marshal Angus Houston, the head of the joint coordination center. It wasn`t clear what the news conference will cover.

HMS Echo has already been searching for sonic transmissions from the flight data recorder in part of the search area. Authorities have said that one alert was experienced but discounted and that false alerts can be obtained from shipping noises or whales.

The Ocean Shield is equipped with the TPL-25, a giant underwater microphone that will listen for the pings from the flight data recorders and the Bluefin-21, an underwater robot that can scour the ocean bed, looking for signs of wreckage.

But until searchers can find a confirmed piece of debris from the plane, which would give them an idea of where the wreckage might be located, the sophisticated listening technology is of little use.

"Really the best we can do right now is put these assets in the best location -- the best guess we have -- and kind of let them go," U.S. Navy Cmdr. William Marks told CNN. "Until we get conclusive evidence of debris, it is just a guess," reports the CNN.

BDST: 0909 HRS, APR 04, 2014