The plane involved in the crash off the Libyan coast was a Shorts SD-360, which has a good safety record as a commuter aircraft.

The Shorts 360 is a twin-engined, propeller-driven plane, manufactured in Northern Ireland.

It had been on its way from Tripoli to the huge petrochemical centre at Marsa el Brega.

Initial reports suggest the aircraft suffered engine failure. David Learmount, operations editor of industry magazine Flight International, said there were two reasons for multiple engine failure.

"One is you run out of fuel," he told BBC News 24. "The other is that there has been a maintenance error, that is that both engines have been under the same maintenance, probably routine and the same error was made on both of them."

The owners of the plane, Swiss air charter company Avisto AG, said it was crewed by two Swiss-trained pilots and one cabin attendant.

It was leased by the Avisto air services company, based near Zurich, to Sirte Oil Company.

'Experienced pilots'

Avisto specialises in aircraft maintenance and repair. It concentrates its operations in North Africa and the Middle East, and operates service flights to oil platforms.

Avisto chairman Franz Fassbind said the aircraft's pilots were trained in Switzerland and were very experienced.

The Shorts 360 is a later model of the 330, a 30-seat utility plane. The design was superseded by the slightly larger Shorts 360 from 1982.

This features a conventional tailplane and fin in place of its predecessor's twin-tail design.

An airliner census by Flight International in 1999 found that there were 82 planes with civil operators of the 330/360 which were at least 15 years old.