UPDATED 7:18am: The search for missing Malaysia Airlines flight MH370 continues, as the families of its 239 victims face their first Christmas without their loved ones.

Australian Transport Safety Bureau chief Peter Foley is leading a team of 180 people in the around-the-clock search in the Southern Ocean.

He says they're absolutely focused on, and prepared for, the task at hand.

"We know the systems that we're using will be effective in detecting the aircraft on the sea floor.

"It is an extraordinary challenge, it's unprecedented but we are confident of success."