TOKYO: Japan Airlines has grounded another one of its Dreamliner jets after “white smoke” was seen outside the cockpit window during maintenance, a year after the aircraft suffered a months-long global grounding over battery problems. The carrier said that a technician at Tokyo’s Narita airport, who was working on the parked plane before its departure to Bangkok on Tuesday afternoon, first noticed what appeared to be smoke outside the cockpit window and then a battery system warning. An investigation found that one of the eight lithium-ion cells in the plane’s battery system had leaked, but its safety valve, which is designed to release excessive pressure, was properly open. “The temperature of the cell was high. We believe it caused ‘white smoke,’ which could be smoke or vapor,” a JAL spokesman said.