The Japan Civil Aviation Bureau is investigating what caused smoke to pour from a main battery vent aboard a Japan Airlines Boeing 787 on January 14. The manufacturer developed a fix for its lithium batteries after last year’s fleet grounding, so the work now is focused on whether the fix actually worked and prevented a larger fire, or whether the smoke and the associated battery alarms were indicative of some other issue. As a precaution, Japan Airlines grounded the 787 involved in the incident.