Four people who died after a helicopter crash off Shetland have been named.
Three of the four bodies have been recovered. Police Scotland confirmed 14 others were rescued.
The Super Puma L2 helicopter crashed west of Sumburgh Airport at about 18:20 BST on Friday.
An investigation into the cause of the tragedy is under way.
RNLI rescue co-ordinator Jim Nicholson said the helicopter - carrying workers from an oil rig - apparently suffered a "catastrophic loss of power".
He said it appeared the aircraft had "suddenly dropped into the sea without any opportunity to make a controlled landing".
"He was by the window so he was able to escape that way as it rolled over," she said.
"He said he had come off better than a lot of people, [those] were his words."
Tim Ripley, an aviation expert with Jane's Defence Weekly, told the BBC there were "many possible scenarios" behind the helicopter crash.
He said: "The most common one at low level for aircraft and helicopters is bird strikes.
"If one of these helicopters ingested a bird it would cause a very, very nasty accident.
"But it doesn't seem like that because we have no reports of collisions, which points towards a failure of the engine and the mechanical systems on the helicopter."
A total of 18 people were on board the helicopter.
PREVIOUS NORTH SEA INCIDENTS
- October 2012 - All 19 people on board a Super Puma EC 225 were rescued safely after it put down in the sea off Shetland. The incident was caused by a cracked shaft in the main gearbox.
- May 2012 - All 14 people on board a Super Puma EC 225 were rescued when it came down about 30 miles off the coast of Aberdeen during a flight to an oil rig.
- April 2009 - All 14 passengers and two crew on board a Super Puma AS332L2 lost their lives after it came down in the North Sea. Eight of the victims came from the north east of Scotland, seven from the rest of the UK, and one from Latvia. A fatal accident inquiry is planned for October.
- February 2009 - A Super Puma EC225 ditched in fog a short distance from a BP oil platform in the ETAP field, 125 miles east of Aberdeen. All 18 people on board survived. Crew error and a faulty alert system were blamed.
The 14 survivors, including the two crew members, were taken to Gilbert Bain Hospital in Lerwick for treatment.
Police Scotland said five were discharged a short time later
and nine were detained overnight either for observation or suffering
from exposure.The ditched helicopter was found broken into several pieces up against rocks.
Boats, including a ferry and a cargo ship, joined lifeboat crews from Lerwick and Aith and helicopters from the coastguard, RAF Lossiemouth and two Bond rescue helicopters to search for survivors.
The AS332 L2 helicopter, carrying passengers crew from the Borgsten Dolphin oil rig in the North Sea, was operated by CHC for Total, taking people to and from oil and gas installations.
Oil firm Total confirmed that the three men and one woman who died all worked for contract organisations.
Stork Technical Services confirmed one its employees, Gary McCrossan, was one of those who had died.
Mike Mann, a senior vice president at the firm, said: "Our heartfelt condolences go out to Gary's family and to all of those affected by this tragedy. We are doing all we can to assist the family at this difficult time."
'Lost power' Earlier, Mr Nicholson told the BBC the helicopter had been in a "fairly inaccessible position... near the cliffs", with weather in the area not "particularly good".
George Allison, 57, Sarah Darnley, 45, Gary McCrossan, 59, Duncan Munro, 46, died in the incident
A CHC spokesman confirmed that an L2 aircraft landed in the water, approximately two miles west of Sumburgh on Friday."The aircraft was on approach to Sumburgh Airport at approximately 6.20pm when contact was lost with air traffic control," he said.
In a later statement, the company said the cause of the incident was unknown but Super Puma L2 flights would be suspended worldwide.
"Also, in deference to the incident and the investigation, we are suspending all flights [on] Saturday by our UK operations," the company added.
Bond Offshore Helicopters also said it would not be operating any of its Super Puma aircraft fleet, with the exception of its Jigsaw rescue aircraft which would be available for life at risk missions.
Michael Bull, whose son Samuel was rescued, said: "We understand he was on his way back from a rig and the helicopter lost power suddenly and immediately ditched into the water.
"He managed to escape straight away because he was right by an exit and I understand soon afterwards that the helicopter turned over."
Investigation team
• NORTH SEA SURVIVAL TRAINING
- All offshore workers are required to undertake offshore safety training, such as emergency first aid, sea survival and helicopter underwater escape training.
- Core courses include Minimum Industry Safety Training (Mist) and Basic Offshore Safety Induction and Emergency Training (Bosiet). Bosiet covers emergency responses on an offshore installation as well as during helicopter transit. The course includes time in a helicopter simulator in a swimming pool.
- Offshore personnel can also undertake Further Offshore Emergency Training (Foet).
- A valid offshore medical certificate of fitness is required for those working in the North Sea.
Police Scotland said a major
incident was declared. The Department for Transport said the Air
Accidents Investigation Branch sent a team to the scene.
Scotland's First Minister Alex Salmond also paid tribute to the "brave and hard-working" people involved in the rescue effort.He added: "Our thoughts at this difficult time are with the families, friends and colleagues of those who lost their lives in this tragic incident."
Oil & Gas UK's chief executive, Malcolm Webb, said: "All offshore helicopter pilots undergo extensive training to prepare them for emergency situations and all passengers undergo regular helicopter evacuation training.
"This incident serves to emphasise the critical importance of such preparation."
He added that helicopter safety remained a focus for the industry, and any lessons that could be learned would be shared across the industry.
Last year, Super Puma helicopters crashed in two incidents, one off Aberdeen and another off Shetland, but these involved the EC 225 variety of the aircraft.
All passengers and crew were rescued in both incidents which were found to have been caused by gearbox problems.
Super Puma EC 225s were grounded following the crashes but were given the go-ahead to resume flying again earlier this month.
Bob Crow, general secretary of offshore union RMT, said workforce confidence in the Super Puma type aircraft was "severely dented" after the two ditching events last year and the fatal accident in 2009.
He said: "RMT and Unite have worked with all sectors of the industry to address the concerns of our members and rebuild that confidence. Last night's events have undone all of that work and we anticipate an outpouring of anger.
The entire Super Puma fleet must remain grounded until the causes of this event are established and dealt with, he said.
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