(Reuters) – Boeing began installing reinforced lithium-ion batteries on five grounded 787 jets in Japan on Monday, starting a process that should make the first commercial Dreamliners ready to fly again in about a week.

Boeing’s Dreamliners have been grounded since regulators in the United States and elsewhere ordered all 50 planes out of the skies in mid-January after batteries on two of them overheated. U.S. regulators approved a new battery design on Friday.

The grounding has cost Boeing an estimated $600 million, halted deliveries and forced some airlines to lease alternative aircraft. Several airlines have said they will seek compensation from Boeing, potentially adding to the plane maker’s losses.

The first five jets to receive the new strengthened battery system all belong to All Nippon Airways , the airline that launched the first commercial Dreamliner service.

“Our first priority is to get the existing fleet back into the air,” Larry Loftis, vice president and general manager of the 787 program, told European reporters.

Ten teams of some 30 engineers each have been dispatched by Boeing worldwide to install the stronger battery casing and other systems designed to prevent a repeat of the meltdowns that led to the first U.S. fleet grounding in 34 years.

The plan approved by the Federal Aviation Administration calls for Boeing to encase the lithium-ion batteries in a steel box, install new battery chargers, and add a duct to vent gases directly outside the aircraft in the event of overheating.

European authorities are expected to follow suit in approving the battery design, a spokesman for Europe’s aviation safety body said.

Although the plane is deemed safe to fly, investigators in the United States and Japan have yet to unravel what caused a 787 battery onboard an ANA jet in Japan and one on another JAL Dreamliner parked at Boston’s Logan Airport to overheat.

“We went to great lengths to question every assumption we made in the initial design and greatly expanded the thought process for what could be potential causes,” Loftis said.

Speaking on the eve of public hearings by the U.S. National Safety Transportation Board, Loftis said Boeing believed it had anticipated “the whole universe of possible causes” after exhaustive studies and testing to devise the battery fix.

“It is possible we will never know the real cause,” he said, “If we learn anything new we will make changes as required.”

Loftis said the crisis would not affect the development of other jets and would not derail Boeing’s plans to double 787 production to 10 a month by the end of the year. Nor would it delay the next version of the 787, known as the 787-9.

“We aren’t changing forecasts for future (787) orders because of this incident,” he said.

Boeing has continued to produce Dreamliners at the rate of 5 a month during the three-month grounding. Deliveries are likely to resume within weeks, Loftis said.

WEIGHT SAVING PARED

The 787 is the first jetliner to be fitted with lithium-ion main power batteries, which are lighter and smaller but potentially more temperamental than the nickel-cadmium sources used on most planes. Batteries are mainly used for ground power.

Loftis said the extra steel housing and other accessories fitted to the batteries to keep them safe weighed about 150 lbs, cancelling out the batteries’ weight savings.

Boeing gave some thought to switching back to traditional nickel-cadmium as rival Airbus has done, but found no reason to do so, he said.

Some aircraft industry sources say space limitations where the batteries are installed on the Dreamliner might have reduced Boeing’s options.

ANA is the world’s biggest operator of the lightweight carbon-composite aircraft with 17 of the planes. After ANA, the biggest 787 operator is local rival Japan Airlines Co  with seven jets, followed by United Airlines and Air India with six each.

ANA plans about 100 to 200 round trip test flights in May of its repaired aircraft before carrying passengers again from June, sources knowledgeable about ANA’s operations have said. The flights will check the safety of the aircraft, and allow ANA’s 180 Dreamliner pilots to get accustomed to flying it again and renew their licenses after more than a three-month break.

ANA has not said how much the 787’s grounding has cost it to date, though it has said it lost about $900,000 in revenue per plane in the last two weeks of January.

In Addis Ababa, a source at Ethiopian Airlines, which had taken delivery of four 787s before the grounding, said they could be flying in a matter of days. Boeing says each battery modification takes about 5 days to install.

SOURCE REUTERS