Another Dreamliner jet is grounded

Japan Airlines has grounded another Dreamliner jet after "white smoke" was seen outside the cockpit window during maintenance, a year after a months-long global grounding over battery problems.

JAL said a technician at Tokyo's Narita airport, who was working on the plane before its departure to Bangkok on Tuesday afternoon, noticed what appeared to be smoke outside the cockpit window and then a battery system warning.

An investigation found 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 vapour," a JAL spokesman said.

The grounded plane was replaced with another Dreamliner, which left as scheduled, carrying 169 passengers and crew.

"We are making sure of the safety of every plane before its departure. We will continue regular flights [with Dreamliners]" said Norihisa Hanyu from the airline.