* Changes not finalized - paper
* Best-case scenario has flights resuming next month
* FAA clears one-off 787 "ferry" flight
* 787 launch customer ANA cancels 1,887 flights for March 1-30
* Japan's major airlines unaware of Boeing's battery plans
Feb 6 (Reuters) - 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, U.S. aviation regulators said they would allow Boeing to make a one-off 787 flight from Texas to the aircraft maker's facility in Washington State, under strict conditions. Boeing said the plane, scheduled for delivery to China Southern Airlines, would be a "ferry" flight - used to relocate a plane without carrying passengers or conducting tests.
Regulators around the world grounded the technologically advanced 787 in mid-January after a battery fire in Boston and a second incident involving a battery on a flight in Japan.
Boeing is looking at changes within the 787's lithium-ion battery to keep heat or fire from spreading, though technical details have not yet been finalized or approved, the Wall Street Journal reported, citing unnamed government and industry officials. One of the paper's sources added that, under a best-case scenario, passenger flights could resume in March.
The Dreamliner's launch customer All Nippon Airways Co Ltd , which has the biggest fleet of the 250-seat planes, said it will cancel 1,887 flights, affecting more than 25,000 passengers, from March 1 to 30. The airline said on Thursday it had no information on Boeing's latest battery plans.
Boeing declined to comment on the newspaper report. GS Yuasa Corp, the Japanese firm that makes batteries for the 787, also declined to comment.
Air safety investigators from the United States and Japan have been investigating the battery incidents for three weeks. On Wednesday, the head of the U.S. National Transportation Safety Board (NTSB) said it was "probably weeks away" from completing its probe.
The NTSB is conducting the U.S. probe with help from Boeing, GS Yuasa, the Federal Aviation Administration (FAA) and battery experts from other U.S. federal agencies. No one has yet identified what caused the battery failures.
In Tokyo, one official said Japanese regulators had not been notified of any breakthrough in the U.S. battery investigation. "The investigation will continue as scheduled. Resuming flights in March ... seems far too optimistic to me," said the official who didn't want to be named as the investigation is ongoing.
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 special FAA-approved conditions to allow 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 authorized 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.
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 787 "ferry" flight. The plane, with a minimum crew, would 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.
Japan Airlines Co Ltd said this week it will talk to Boeing about compensation for the 787's grounding, which it expects to cost nearly $8 million from lost earnings through March. ANA has said it would seek compensation from Boeing once the amount of damages was clearer.
JAL said on Thursday it was also unaware of any Boeing plans to test new batteries.