Updated

Boeing Co.'s chief engineer for the 787 Dreamliner says changes to the lithium-ion battery are fully sufficient to ensure the aircraft's safety, although the company has been unable to find the cause of the original battery failures earlier this year that led to groundings of the plane worldwide.

U.S. and Japanese regulators have given carriers permission to resume 787 flights after battery modifications are made.

The new battery system is designed to prevent a fire, and to contain one should it occur by encasing the battery in an "enclosure," Michael Sinnett told a news conference Saturday in Tokyo.

"Even if we never know the root cause, the enclosure keeps the airplane safe, it eliminates the possibility of fire, it keeps heat out of the airplane," he said.