Agency inspectors will oversee Boeing's work in adjusting the planes, the agency said, and both the FAA administrator, Michael P. Huerta, and Transportation Secretary Ray LaHood said they are satisfied that the proposed changes will eliminate concerns that the plane's two lithium-ion batteries could catch fire.
The changes "will ensure the safety of the aircraft and its passengers," LaHood said Friday.
The decision was a major milestone for Boeing and its innovative jet. Aviation analysts said the battery problems this year cost Boeing hundreds of millions of dollars and slowed its progress in fielding the planes, which reduce fuel costs by 20 percent and have been in great demand by airlines.
Boeing's shares rose more than 2 percent Friday, closing at $87.96 a share.
The 50 jets delivered so far were grounded worldwide after two incidents in January in which the volatile batteries caught fire or emitted smoke. Boeing has said the new battery systems are ready to go, and it will install them on the planes it has already delivered before changing the jets still in production.
Boeing's fix includes more insulation between each of the eight cells in the batteries. The batteries also will be encased in a steel box designed to contain fire and vent possible smoke or hazardous gases out of the planes.
"The Boeing team is ready to help get our customers' 787s back in the air where they belong," said Ray Conner, who runs Boeing's commercial airplane division.
The FAA said that next week it will sign off on specific instructions that Boeing is preparing for the airlines on how to handle the battery system. The FAA also will publish a final directive that would effectively lift the grounding order issued in January.
Aviation regulators in other countries must also weigh in and approve the system. About half of all 787s delivered so far are operated by two Japanese airlines.
The Japanese transportation minister, Akihiro Ota, said Friday in Tokyo that Japan's own assessment of the safety of Boeing's battery changes was "in its final stages."
"We're doing our best to ensure a safe and speedy return to service," he said.
But Japanese regulators could ask Boeing for additional safeguards, the Nikkei business daily reported Friday.
Japanese regulators remain concerned that investigators have not pinned down precisely why the batteries overheated in the first place.