The hunt for missing Malaysia Airlines Flight 370 in a remote patch of the Indian Ocean is progressing well but is likely to take many months because of the huge area involved, Australian officials said.

Search co-ordinator Peter Foley said there is optimism with two ships using high-tech sonar devices to search for the Boeing 777, which disappeared in March while flying from Kuala Lumpur to Beijing with 239 people on board.

He said weather is improving and they hope to cover as much area as possible.

Mr Foley said that given the size of the search area "we are in for the long haul", adding that: "It will take many months."

Despite a massive air and sea search, not a single piece of debris from the plane has been found.