WASHINGTON (REUTERS) - A US appeals court on Friday (Jan 10) upheld a lower court decision to dismiss nationwide litigation over the disappearance of Malaysia Airlines Flight MH370 in which victims' families sought to hold the carrier, its insurer Allianz and Boeing liable for the still-unexplained disaster.

A three-judge panel of the US Court of Appeals in Washington affirmed a November 2018 ruling from US Judge Ketanji Brown Jackson that found 40 wrongful death and product liability lawsuits "do not belong in the United States."

Judge Neomi Rao, writing for the unanimous panel, said that while the court "has great sympathy for the victims of this tragedy and their families" she found no reason to reverse the decision.

"We conclude that the district court did not clearly abuse its discretion in dismissing appellants' lawsuits," she wrote.

Jackson said the case belonged in Malaysia, which has an"overwhelming interest" in and "substantial nexus" to the March 8, 2014 disappearance of Flight MH370, a Boeing 777 heading to Beijing from Kuala Lumpur with 239 people on board.

The decision is a new setback for plaintiffs from the United States, Australia, China, India and Malaysia who represented more than 100 Flight MH370 passengers, including from Japan.

The plane is believed to have crashed in the south Indian Ocean after veering far off course, but no remains or large pieces of wreckage have been found.

Flight MH370's disappearance remains one of the world's greatest aviation mysteries.

A Malaysian report concluded that its investigative team was "unable to determine the real cause for the disappearance of MH370"; human interference or error were more likely the cause of the plane's disappearance than aircraft or system malfunction.

The plaintiffs sued under the Montreal Convention, an international treaty governing air transportation incidents, and various US state laws.