Japan's two biggest airlines Wednesday took half the global 787 Dreamliner fleet out of service on safety grounds after an emergency landing by an ANA flight brought new trouble for Boeing's cutting-edge plane.
But carriers including All Nippon Airways insisted that the fuel-efficient airliner was still a safe bet, despite several incidents that have prompted investigations by US and other aviation regulators.
ANA -- the world's first carrier to receive the Dreamliner from Boeing after years of delays -- said smoke possibly stemming from a faulty battery forced the pilots to land the passenger plane in Takamatsu, southwestern Japan.
The airline said cockpit instruments had detected the smoke inside a forward electrical compartment, and Japanese Transport Minister Akihiro Ota called it a "serious incident that could have led to a serious accident".
One of the 129 passengers on the Tokyo-bound domestic flight was quoted by broadcaster NHK as saying he "smelled something strange" after take-off and feared the plane was going to crash.
Nobody was seriously injured however when the passengers and eight crew members evacuated via emergency chutes.
ANA and its rival Japan Airlines (JAL) -- among Boeing's biggest customers for the Dreamliner -- said they would ground their entire 787 fleets through Thursday at least, pending safety checks.
ANA has 17 Dreamliners and JAL has seven -- half the 49 planes currently in operation worldwide. Boeing has orders for nearly 850.
The Dreamliner is considered an aviation milestone with its extensive use of lightweight composite materials and electronics, instead of aluminium and hydraulics, and airlines have embraced the plane as a way to save on high fuel costs.
But a week of mishaps leading up to the forced landing in Japan has generated unwelcome headlines for Boeing -- which says it has "complete confidence" in the plane and is pledging to work with its customers and regulatory agencies.
In addition to fuel leaks and a cracked cockpit window involving 787s in recent days, there was a battery fire and smoke on an empty JAL-operated Dreamliner on the ground in the US city of Boston last week.
JAL said that event involved a battery used for the Dreamliner's auxiliary power unit, located at the rear of the plane. Wednesday's incident involved the forward battery for the main power unit, ANA said.
"After examining the fuselage, we confirmed that inside the forward electrical equipment bay the main battery has been discoloured and the electrolyte solution has leaked," it said in a press release.
"We've only been using these aircraft for a year and we don't have enough information about the cause. That's why we decided to stop using these planes for the moment," ANA vice president Osamu Watanabe told a news conference.
Both the US Federal Aviation Administration (FAA) and Japan's transport ministry broadened existing Dreamliner probes to encompass the latest incidents. Authorities in India said they were starting their own investigation.
Shukor Yusof, an aviation analyst with Standard and Poor's Equity Research in Singapore, said Boeing would suffer a "huge" blow if the FAA ordered structural changes to the Dreamliner, but added: "We are nowhere near that stage."
Noting teething troubles with Airbus's A380 superjumbo, he said that technical glitches were not unusual with new planes but nonetheless described the problems as "very embarrassing" for Boeing.
Despite the grounding, ANA said it stood by billions of dollars committed to future 787 orders.
The Dreamliner also received backing from other carriers that have bet on the project, with British Airways, Air France, Singapore Airlines, Australia's Qantas and Korean Air all affirming pending orders.
British Airways, which has 24 Dreamliners on order, reaffirmed a statement from last week that it was "committed to taking delivery of the aircraft". A spokesman for Air France said its order of 25 of the aircraft beginning in 2016 "hasn't been called into cause."
Public confidence in the Dreamliner may have been dented, however, after production setbacks among Boeing's large array of subcontractors -- many of them Japanese -- delayed delivery of the first plane to ANA by three years to 2011.
"This morning, I heard the news and I got a bit scared. I checked that my flight wasn't on a Boeing 787," said Tomohiko Maruyama, who spoke to AFP as he waited to board an ANA flight at Tokyo's Haneda airport.