The bad news keeps coming for Boeing, whose 787 Dreamliner fleet remains grounded—US investigators still don't know what caused the battery fire in a Jan. 7 fire in Boston, reports Reuters. The National Transportation Safety Board says it has found a series of "symptoms" in the battery, but are nowhere near knowing the underlying cause. The NTSB chair would not say how long the investigation might take, but a former NTSB chair predicts, "It's going to take them longer. Weeks, not days."
Investigators are concerned that back-up protections designed to prevent a "thermal runaway"—a chain reaction causing the battery to overheat—did not work, reports the Los Angeles Times. "There are multiple systems to protect against a battery event like this," says the current NTSB chair. "Those systems did not work as intended."