WASHINGTON (AFP) - Boeing's 787 Dreamliner is suffering serious teething problems that have grounded the plane in Japan and stoked market concerns about the US aerospace giant.

All Nippon Airways grounded its 787 fleet Wednesday after smoke in an electrical compartment forced an emergency landing. Japan Airlines followed suit. The combined 24 planes will be grounded at least through Thursday for safety checks.

The two Japanese airlines account for almost half of the 50 787s already in service, and Boeing had hoped their fleets would serve as a shop window for a new model on which it has staked much of its business strategy.

It was the seventh safety incident with the high-tech plane - marketed by Boeing as the fuel-efficient future of aviation - experienced by ANA and JAL in less than two weeks.

The mishaps included a fire in an unoccupied stationary aircraft, fuel leaks and a cracked cockpit windshield.

Until now, the rash of problems had not dented investor confidence in the aerospace giant. Since the first incident this year, on Jan 7, until the market closed Tuesday, Boeing's share value had climbed 0.6 per cent.

But on Wednesday, Boeing shares plunged 3.4 per cent in New York, dragging down the Dow Jones Industrial Average.

"The one thing that must send shudders through Boeing Co. management and its board is that the 787 Dreamliner could be taken out of service because of a series of accidents," said Mr Douglas McIntyre of 24/7WallSt.com.

"Boeing engineers, aircraft experts and several Wall Street analysts have defended problems with the jet as routine for a new airplane. The power of those defences is now over," he added in a research note.

Boeing has staked its future on the all-new aircraft, which is heavily equipped with electronics. Lightweight composite materials, to boost fuel efficiency, comprise 50 per cent of the Dreamliner.

The Chicago-based company has ramped up 787 production to five airplanes per month and plans to make 10 a month by late 2013.

Boeing, which touts the 787 as the most successful twin-aisle launch of a commercial plane in the company's history, says it has more than 800 unfilled orders with 58 customers worldwide.

24/7WallSt's McIntyre warned that the pileup of incidents could threaten Boeing's order book.

"Boeing must now contend with the issue that other large airlines that use the Dreamliner, or are about to take delivery, will ground the planes as well." Rich Smith at The Motley Fool said "the facts about the Dreamliner's safety are starting to stack up - and not in Boeing's favour."

Smith noted that the nearly 850 Dreamliners sold around the globe represent one out of every five airplanes in Boeing's mammoth 4,373-plane-long order backlog.

"None of this - needless to say - is going to be particularly good news for Boeing's 787 sales force," he added.

Loren Thompson of the Lexington Institute said the 787 was experiencing problems any new airplane might face.

"However, the decision of regulators to launch a review of the plane increases the visibility of the plane in a way that might hurt sales," Thompson said.

US regulators launched on Friday an in-depth safety review of the Dreamliner after the unusual number of safety incidents. The Federal Aviation Administration said it was working with Boeing to review critical systems, particularly the electrical systems.

Both the FAA and Boeing have expressed confidence in the plane, echoed by a number of airlines.

United Airlines, the only US carrier flying the 787, said Wednesday it had inspected all of its 787 aircraft and that they were flying as scheduled.

"We are continuing to support Boeing and the FAA throughout their review," the world's biggest airline said.

After the ANA emergency landing, the FAA said it would include the incident in its review. The National Transportation Safety Board announced it would send an investigator to Japan this week to assist in the Japanese authorities' investigation.

Deutsche Bank analysts said: "The hits just keep coming for the 787."

"The bigger issue is that FAA and Boeing want to walk away with 1) a safe airplane and 2) credibility in the initial certification process," they said.

Barclays analysts highlighted that with limited data and company commentary amid ongoing investigations in the US and Japan, "it could be difficult for shares to gain near-term traction."