U.S. and European regulators have already approved Boeing’s plans to add safety features to the 787’s lithium-ion batteries that would minimize the odds that they would emit smoke or catch fire, after two units overheated on separate planes in January.

Late Friday, the Japanese Ministry of Transport followed suit, authorizing All Nippon Airways and Japan Airlines — which together own about half of the 50 Dreamliners delivered — to resume flights of a plane whose grounding has affected tens of thousands of passengers.

The ministry is asking All Nippon and Japan Airlines to adapt voluntary safety measures, including adding monitors to the batteries to read voltage levels in real time, before the planes are brought back to service.

Akihiro Ota, the transport minister, said at a news conference earlier Friday that he was satisfied with the multiple measures Boeing had taken to eliminate risks of fire. “They have adopted defense in depth,” Mr. Ota said.

All Nippon said that teams of Boeing engineers had already started to replace batteries on all of its 17 Dreamliners and that fixes would take until the end of May to complete. The airline said it would start using the planes again for commercial flights when the fixes had been made to its entire fleet. Japan Airlines declined to speculate on how long the fixes would take.

All Nippon said its 787s would each undergo a test flight to “confirm that no battery-related failures occur during flight.” The first test flight is scheduled for April 28, the Tokyo-based airline said in a statement.

The airline will also install improved battery monitoring systems on its planes and put its 787 cockpit crews through additional in-flight training. After the planes are back in service, the airline will remove a sample of batteries to inspect to make sure the improvements are effective, All Nippon said.

All Nippon said it intends to set up a dedicated Web site to address passenger concerns about the safety of the 787.

“Only when we are fully satisfied with the safety of our 787 fleet will we return the aircraft to service,” Osamu Shinobe, president and chief executive of All Nippon, said in a statement.

U.S. and Japanese regulators have been investigating the Japanese-made batteries aboard the 787 after one caught fire aboard a parked plane in Boston operated by Japan Airlines and another emitted smoke during an All Nippon flight in Japan, forcing an emergency landing. The incidents prompted regulators to ground the entire 787 fleet.

Norihiro Goto, the head of the Japan Transport Safety Board, said earlier this past week that investigators remained unsure what had caused the batteries to overheat. But Japan was satisfied that Boeing had now considered all conceivable potential problems that could lead to a battery fire, Mr. Goto said.

Japanese airlines have been enthusiastic buyers of the 787, Boeing’s latest-generation, fuel-efficient plane. It is the first passenger jet to use lithium-ion batteries, which are more powerful, easier to charge and lighter than older battery technologies. But they have also proven to be prone to overheating.

Article source: http://www.nytimes.com/2013/04/27/business/global/27iht-dreamliner27.html?partner=rss&emc=rss