US regulators have approved a revamped battery system for Boeing's 787 Dreamliner, a crucial step in returning the plane to service after more than three months of grounding prompted by lithium-ion batteries that burned on the jets.

The Federal Aviation Administration (FAA) said on Friday that it had approved a package of detailed design changes, a move that allows Boeing to issue a service bulletin and make repairs to the fleet of 50 planes owned by eight airlines around the world.

"Next week, the FAA will issue instructions to operators for making changes to the aircraft and will publish in the Federal Register the final directive that will allow the 787 to return to service with the battery system modifications," the agency said. "The directive will take effect upon publication.

"The FAA will require airlines that operate the 787 to install containment and venting systems for the main and auxiliary system batteries, and to replace the batteries and their chargers with modified components."

At this time, the FAA announcement only affects United Airlines, the sole US airline flying 787s.

The FAA said it would "continue to support other authorities around the world as they finalise their own acceptance

Boeing, which has been working with the FAA and other regulators to discover the cause of the battery problems and
develop a fix, welcomed the FAA's approval.

"This is a comprehensive and permanent solution with multiple layers of protection," said Boeing commercial
airplanes president and chief executive Ray Conner.

A report on Friday suggested regulators in other countries could impose additional safety requirements on Boeing.

The article in Japan's Nikkei business daily said measures imposed by the Japanese transport ministry could include remote monitoring of battery data such as voltage and more frequent battery inspections.

All of the 50 Boeing 787 planes in service were grounded globally in mid-January after a series of overheating problems with the cutting-edge plane's lithium-ion battery system.

The grounding came after a battery fire on a parked Japan Airlines 787 at Boston's Logan International Airport and an incident in which battery smoke forced an emergency landing of an All Nippon Airways 787 in Japan.

Source: Agencies