Japan has said it is too early to estimate when Boeing's 787 Dreamliners can resume operations, despite an announcement from the US aircraft manufacturer's saying it could have the grounded jets flying again in a matter of weeks.
"At this time we are not yet in a position to say when flights will restart," said Shigeru Takano, air transport safety director at Japan's Civil Aviation Bureau, following the US aircraft manufacturer's comments.
Boeing unveiled on Friday its proposed fix for the aircraft's battery system that it says will eliminate the risk of fire.
"I would gladly have my family, my wife and my children, fly on this airplane"
- Mike Sinnett, chief project engineer for the 787 programme
In its first detailed explanation of the proposed changes to the system, the company said it would encase the 787's lithium-ion battery in stainless steel and fit the power pack with extra insulation, spacers and heat-resistant sleeving.
"If we look at the normal process and the way in which we work with the [US Federal Aviation Administration (FAA)], and we look at the testing that's ahead of us, it is reasonable to expect that we could be back up and going in weeks, not months," Mike Sinnett, chief project engineer for the 787 programme, told reporters at a briefing in Tokyo.
Regulators grounded all 50 of the carbon-composite Dreamliners in use by airlines worldwide in January after a battery caught fire on a Japan Airlines 787 jet at Boston's Logan airport and a battery melted on an All Nippon Airways flight in Japan.
Japan is Boeing's biggest customer for the fuel-efficient aircraft, which has a list price of $206m, with Japan Airlines and All Nippon Airways accounting for almost half of the Dreamliners delivered to date.
Earlier this week, the FAA approved Boeing's plan to fix the battery system, starting what could be a rigorous testing regimen.
The company also faces US public hearings in April on the safety of its lithium-ion batteries.
Boeing is now about a third of the way through the certification process of the new battery, the company said.
"This enclosure keeps us from ever having a fire to begin with," Sinnet said of the new battery's casing.
Boeing has said the proposed changes to the battery and its testing plans are a final fix. But it remains unknown what effect the 787 problems have had on public perception of the plane's safety.
"I've flown on the 787 more than 100 times, and I never once had any concern about my safety. I would gladly have my family, my wife and my children, fly on this airplane," Sinnet said.