US aviation authorities gave Boeing Inc the go-ahead to begin testing changes Tuesday to troubled battery systems on the aerospace manufacturer's new 787 Dreamliners, which have been grounded since January, dpa reported.
Boeing chairman and chief executive Jim McNerney called the Federal Aviation Administration's approval a "critical and welcome milestone toward getting the fleet flying again."
Overheating and short-circuiting problems with the lithium-ion batteries, which are used in part to boost the Dreamliner's fuel efficiency, have kept the 49 Dreamliners already delivered to airlines grounded since January 16, after two incidents during and after flights.
Hundreds more Dreamliners are due to be delivered in the coming years to airlines around the world, making the grounding an expensive and embarassing problem for Boeing.
Boeing is implementing several changes in the batteries to prevent future problems and is conducting a "comprehensive series of tests will show us whether the proposed battery improvements will work as designed," US Transportation Secretary Ray LaHood said.
"We won't allow the plane to return to service unless we're satisfied that the new design ensures the safety of the aircraft and its passengers.
Engineers have yet to fully explain why a battery caught fire on a Dreamliner after landing in Boston, and a second plane was forced to land in Japan when a battery melted.
No schedule was immediately set for the Dreamliners to return to service.