Battery expert Dan Doughty also said batteries almost never self-combust.

"You can never say never. But it is almost impossible to have a thermal runaway that would cause the combustion that you're talking about," he said.

Lithium-ion battery failures during use "are very rare," said Doughty. "The statistics that we have are on computer batteries. And the cells that go into computer batteries have a failure rate of one in 10 million or even one in 40 million cells. So it's quite rare," he said.

However, the fire incidents aboard the two Dreamliners very early in the plane's life has raised concern among safety experts.

Boeing has said its technical experts are working "around the clock" and are focused on "resolving the issue" and returning the 787 to service.