Patricia Gayer, from Cardiff, lost her sister Caroline Depledge, brother-in-law Norman, nephew Michael and niece Jane.

The Depledges were among 229 passengers and crew - 11 of them Britons - who died when Swissair Flight 111 crashed into the sea off the Canadian coast last September.

The plane, from New York to Geneva, disappeared from radar screens off Peggy's Cove in Nova Scotia.

Flight 111 disappeared from radar screens off the Canadian coast

Canadian and Swiss accident investigators have yet to determine why the Boeing/McDonnell Douglas MD-11 plunged into the sea.

Concerns about wiring

In March the US Federal Aviation Administration ordered all MD-11 planes of the same type as Flight 111 to undergo wiring inspections.

Swissair has already offered the equivalent of £84,000 in compensation to the victims.

The Depledges lived in Concord, Massachusetts, where Mr Depledge worked for the US computer company Compaq. Mr Depledge, a graduate of Manchester University, took his family to the US in the 1970s.

They were on their way to Europe for a climbing holiday in the Swiss Alps.

The voice recorder was recovered but yielded few clues

Michael, 31, worked for a computer company in California while his 28-year-old sister, a graduate of Yale, was studying for an advanced law degree in New York.

Mrs Gayer has declined to comment on her reasons for launching the lawsuit, which is believed to be one of at least 20 which have been filed.

'Serious risks'

But her lawyer Sean McCarthy told the Boston Herald newspaper: "There were serious risks in flying on that plane.

"We have alleged the defendants were aware of those risks and we intend to prove that."

Mr McCarthy said the lawsuit alleged both the manufacturer and the airline knew the plane had "potentially deadly electrical flaws".

He told the Boston Herald: "The parents had been planning for a comfortable retirement and the children were embarking on careers with tremendous potential. It is a tragedy."

Boeing spokesman John Dern declined to comment on the lawsuits and said his company was "continuing to support the investigation which is being held by the Canadian authorities."