The U.S. National Transportation Safety Board is examining the certification and testing of the lithium-ion battery system on the Boeing Co (BA.N) 787, but still has not found the root cause of a January fire, the board said on Thursday.
The NTSB's "interim factual report" includes extensive detail on the testing done on the burned battery, but it also made clear that investigators are still a long way from understanding why it happened in the first place.
The U.S. Federal Aviation Administration is considering a proposal by Boeing to address the risks of fire aboard the plane. FAA approval could come within days, according to sources familiar with the plan.
The NTSB report marks a milestone in the agency's probe into one of two lithium-ion batteries that burned on 787 jets in January. The U.S. incident occurred on a plane parked at Boston's Logan Airport. Japanese regulators are investigating the second incident.