Boeing Co on Friday gave US aviation regulators its plan to fix the volatile battery aboard its new 787 Dreamliner, even though investigators have not yet determined what caused the batteries to overheat on two planes last month.

Boeing did not propose abandoning the lithium-ion batteries and is not working on a backup or longer-term fix for the problem that has grounded its entire fleet of 50 Dreamliners for nearly five weeks, three sources familiar with the plan said.

The company and the US Federal Aviation Administration said no firm result emerged from the meeting between Deputy Transportation Secretary John Porcari, FAA Administrator Michael Huerta and other FAA officials and Boeing Commercial Airplanes CEO Ray Conner and other senior Boeing executives in Washington.

With Boeing's costs mounting by millions of dollars a day while the planes are on the ground, the FAA said it is "reviewing a Boeing proposal and will analyze it closely. The safety of the flying public is our top priority and we won't allow the 787 to return to commercial service until we're confident that any proposed solution has addressed the battery failure risks."

The proposal to the FAA includes measures to address a range of possible causes of short-circuits in the batteries, the sources said.

Five weeks ago, US authorities grounded the worldwide fleet of 787s. US, Japanese and French investigators are still not certain what caused the battery fire aboard an All Nippon Airways 787 in Boston and an overheated, smoking battery on a Japan Airlines 787 in Japan.

Reuters