Tokyo ( CNN ) -- Japan has authorized passenger airlines to resume flights of Boeing 787 Dreamliners in the country starting Friday , authorities said . The move follows the U.S. Federal Aviation Administration 's online posting Thursday of a directive outlining the modifications necessary for the Dreamliner to fly again after faulty battery systems grounded the aircraft earlier this year . The directive goes into effect upon publication Friday in the U.S. Federal Register . The Japanese transport ministry said All Nippon Airways and Japan Airlines , the world 's two largest Dreamliner operators , have already begun installing modified lithium ion batteries on their 787 jets . But it remains unclear precisely when the two airlines will resume scheduled passenger flights of the Boeing planes . Nearly 50 Dreamliners around the world have been grounded for more than three months , after two incidents on jets operated by the Japanese airlines called the battery systems into question . Last week , the FAA cleared Boeing to make fixes to the problematic battery system . Boeing said it was deploying teams to help the airlines install the redesigned system . The Dreamliner 's use of lightweight composite materials to greatly improve fuel economy has made it a big seller in Asia and the Middle East , where long-haul flights account for much of an airline 's business . Dreamliners inching toward the runway .
The Japanese decision followed a request from Japanese government officials . Japanese airlines , the biggest Dreamliner operators , are installing new batteries . It is unclear exactly when they will resume operation of the Boeing planes .