Those searching for missing Malaysia Airlines Flight MH370 face tough choices on how to proceed after almost seven fruitless weeks, with only a fraction of a deep-sea zone still left to be scanned.

After 11 dives seeking wreckage from the Malaysia Airlines jet, which mysteriously disappeared on March 8, an autonomous underwater vehicle has come up empty-handed.

"Bluefin-21 has now completed more than 90 percent of the focused underwater search area," the Joint Agency Coordination Centre (JACC) managing the search said early Thursday.

"No contacts of interest have been found to date."

Australia is leading the search for the missing Boeing 777, which is believed to have crashed in the southern Indian Ocean after veering dramatically off course from its Kuala Lumpur to Beijing route.

JACC refused to speculate on what the next steps would be if Bluefin-21 ended its 3D sonar scanning mission, but said the search would continue.

"We are currently consulting very closely with our international partners on the best way to effect this for the future," it said.

For now, it will not give up on the 400 square kilometers  search zone which has offered the best hopes so far of finding the aircraft, based on seabed signals consistent with those emitted by black box data recorders.

"At the moment, we are focused on pursuing the best lead we have in relation to missing Flight MH370," JACC said.

The Australian Transport Safety Bureau has reportedly suggested that the search zone could be broadened, if calculations about the plane's position when it likely ran out of fuel and crashed are revised.

"The area for focus of the search ... has already been moved twice, and there's always a possibility that further work will move it again," the bureau's Chief Commissioner Martin Dolan told CNN.

The visual search has for days been frustrated by weather related to ex-tropical Cyclone Jack, which is one of the possibilities Dolan said could suspend the search again.