A fatal accident inquiry is to be held into a helicopter crash which killed four people near Shetland.

A total of 18 people were on board when the Super Puma crashed on its approach to Sumburgh in 2013.

Passengers Sarah Darnley, 45, from Elgin in Moray, Gary McCrossan, 59, from Inverness, Duncan Munro, 46, from Bishop Auckland in County Durham and George Allison, 57, from Winchester, died.

A date for the inquiry has yet to be decided.

A Crown Office spokesman said: "In coming to this decision Crown Counsel have considered the available evidence, the recommendations of the COPFS Helicopter Incidents Investigation Team, and expert opinion.

"The investigation by the police, with officers working closely with the COPFS Helicopter Team, has been complex and challenging. COPFS will now work closely with the Scottish Courts and Tribunals Service (SCTS) to make suitable arrangements for holding the inquiry.

"COPFS will continue to keep the relatives of the deceased informed of significant developments."

Ms Darnley is believed to be the first woman killed in a North Sea oil industry helicopter crash.

Her mother previously told STV news of her frustration for a date not being set for the inquiry.

"Well it wouldn't make any difference to us because they're not coming back, but it would just finish it," she said.

"And that's what we want - for it to be finished with and get on."

Air accident investigators found that decreasing airspeed had gone unnoticed by pilots before the crash.