Boeing's beleaguered 787 could be flying again within a week after US officials approved a fix for its batteries, even though the root cause of a fire on one plane and smoke on another is still not known.
The Federal Aviation Administration said on Friday it would send airlines instructions and publish a notice next week lifting the three-month grounding order.
Airlines will be able to begin fly-ing the planes again as soon as the new systems are installed and they have approval from safety regulators in their own countries.
Dreamliner flights could resume within a week, the agency told members of Congress.
Qantas' budget offshoot, Jetstar, had been due to take delivery of the first of 14 Dreamliners in August, although the airline has said there could be a couple of months' delay.
Boeing is eager to get the planes flying. It has stationed 300 workers on 10 teams around the world to do the work, some of it beginning on Friday, 787 chief engineer Mike Sinnett said. It will take about five days to install the revamped lithium-ion battery system on each plane, he said.
The FAA gave Boeing permission last month to test the revamped system, which includes additional insulation around each of the battery's eight cells to prevent a short circuit or fire in one of the cells from spreading to the others. The new system also includes enhanced venting of smoke and gas from inside the battery to outside the plane. A strengthened box to hold the battery is an effort to ensure that if a fire were to occur, it would not spread.
Boeing has completed 20 separate tests of the new system, FAA administrator Michael Huerta told Congress last week.
The system involved in the emergencies in January had been extensively tested, too.
"We always learn more as we dig deeper into things," Mr Sinnett said. "We have learnt a lot about how to test batteries, and to be conservative" in testing.
Boeing had delivered 50 planes to eight airlines in seven countries when a fire erupted in a battery aboard a Japan Airlines 787 parked at Boston's Logan International Airport on January 7.
Nine days later another incident forced an emergency landing in Japan by an All Nippon Airways 787. That prompted the FAA and other authorities to ground the entire fleet.
Boeing said new batteries and kits with the parts for the new battery systems had been shipped to Boeing centres around the world and were ready to be installed.