Malaysia's transport minister says if Malaysia Airlines Flight 370 is not found by the end of May, the three countries leading the search in the southern Indian Ocean will re-examine data and come up with a new plan.

Liow Tiong Lai told a select group of foreign reporters on the eve of the anniversary of the plane's disappearance during a flight from Kuala Lumpur to Beijing that he remains cautiously optimistic that the Boeing 777 should be in the area where the underwater search has been ongoing.

He said Saturday that Australia, Malaysia and China were due to meet next month to discuss the search efforts.