The US airline regulator has approved a plan to redesign the lithium-ion batteries of the Boeing 787 Dreamliner.
The Federal Aviation Administration (FAA) approved Boeing's plan, which it said requires it to "conduct extensive testing and analysis".
But the FAA gave no indication of when the planes might be allowed to carry passengers again.
All 50 Dreamliners in operation were grounded after the batteries emitted smoke on several separate occasions.
The plane is the first plane in the world to use the lithium-ion batteries, which are lighter, hold more power and recharge more quickly.
The FAA has also approved limited test flights for two aircraft to test the changes in the batteries.
"This comprehensive series of tests will show us whether the proposed battery improvements will work as designed," said US Transportation Secretary Ray LaHood. "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."