A Boeing executive on Friday declined to answer questions about Dreamliner's growing list of problems less than two weeks after another grounding, as he touted the troubled aircraft's new models.
A Qatar Airways 787 Dreamliner resumed flights on Wednesday after being grounded due to what the US plane manufacturer said was the replacement of "technical components".
The plane was out of action from July 22, an industry source told AFP.
The fuel-efficient plane has suffered a string of woes largely tied to its lithium-ion batteries, including a four-month worldwide grounding at the start of the year and a fire onboard an empty Ethiopian Airlines plane at London's Heathrow airport last month.
On Friday, Scott Fancher, vice president and general manager of airplane development at Boeing, told a Tokyo press briefing that the firm was preparing to introduce new versions of its 787 Dreamliner as well as the long-range 777 and smaller 737.
The company was planning a test flight of its larger and more energy efficient 787-9, due to come into service next year, he said, adding that its successor would likely be in the air by 2018.
But Fancher declined to discuss the current Dreamliner's problems or the battery system on its revamped model. Japanese battery maker GS Yuasa has been the global supplier for powerpacks in Boeing's Dreamliner.
"It is a detailed design question, not the sort of thing we are talking about," Fancher said in a response to a reporter's question about the Dreamliner battery.
"I'm not going into a lot of detail on design details," he added.
Despite a lengthy investigation, Boeing has not identified the root cause of the Dreamliner's battery problems, but said it put safeguards in place to prevent future incidents.
Japan's two biggest airlines, All Nippon Airways and Japan Airlines, were sideswiped by the grounding of Boeing's new aircraft that began in January, forcing them to cancel hundreds of flights until the plane was allowed to resume flying in June.
The pair, which have been the Dreamliner's biggest customers, have so far stuck with the plane, saying it was key to their expansion drive.
But the carriers are in talks over compensation for what they said was more than $200 million in combined lost revenue from the grounding.