Boeing Co is working on battery design changes that would minimize fire risks on its grounded 787 Dreamliner and could have the passenger jet flying again as soon as March, the Wall Street Journal reported on Wednesday.
Separately, US aviation regulators said they would permit Boeing to make a special one-time 787 flight from Texas to Washington state, albeit with heavy conditions.
Regulators around the world grounded the technologically advanced 787 on January 16 after a battery fire in Boston and a second incident involving a battery on a flight in Japan.
The newspaper, citing unnamed government and industry officials, said Boeing was looking at changes within the lithium-ion battery to keep heat or fire from spreading. Technical details have not yet been finalised or approved, though, the paper's sources noted.
One of the paper's sources added that, under a best-case scenario, passenger flights could resume next month.
Boeing declined to comment on the report. GS Yuasa Corp, the battery's maker in Japan, also declined comment.
One source familiar with the investigation told Reuters that Boeing engineers sprang into action "almost immediately" after the first battery incident to ensure the company could meet the FAA-approved "special condition" that allowed lithium-ion batteries on the aircraft.
"They can't afford to sit around with their planes on the ground," said the source, who was not authorised to speak publicly.
Boeing was pursuing multiple solutions to mitigate and contain a fire if one started in the batteries, part of a determined effort to get the 787s back in the air while a more permanent solution - possibly even a different battery - was explored.
Three or four different approaches would be pursued to ensure the batteries did not breach their containment systems, even if they caught fire, said the source.
Earlier on Wednesday, the head of the US National Transportation Safety Board said it was "probably weeks away" from completing its probe.
The NTSB is conducting the US probe with help from Boeing, GS Yuasa, the Federal Aviation Administration and battery experts from other US federal agencies. None of the agencies have identified what caused the battery failures on the 250-passenger jetliner.
The NTSB is investigating the battery failures, but the Federal Aviation Administration would have to certify any "fixes" Boeing proposed.
Boeing asked the FAA this week for permission to conduct new test flights of the 787, suggesting it is making progress in finding a solution to the problems, but the government agency has not yet announced a decision.
While that request is pending, the FAA said on Wednesday it would allow a one-time "ferry" flight of a 787 to Washington. The plane will fly with a minimum crew and will have to land immediately if the flight computer displays any battery-related messages. It was not immediately clear when the flight would take place.
Some 50 Dreamliners have been grounded while investigators try to solve the battery mystery, which has cost airlines tens of millions of dollars already.
Earlier this week Japan Airlines Co Ltd said it will talk to Boeing about compensation for the grounding of the 787 Dreamliner, adding that the idling of its jets would cost it nearly $8 million from its earnings through to the end of March.
Rival All Nippon Airways, which has more 787s than JAL, said last week it would seek compensation from Boeing once the amount of damages was clearer.
ANA said it had no information on Boeing's latest battery plans.