A helicopter carrying 19 people has ditched in the North Sea, Aberdeen Coastguard said.
All 19 passengers and crew have been accounted for, but it is not yet known what their condition is.
It is understood the helicopter made a "controlled ditching" into the sea.
Three lifeboats have been launched from Kirkwall in Orkney and Aith and Lerwick in Shetland, the RNLI said. Three helicopters are also involved in the search which is being co-ordinated by Shetland Coastguard.
Other vessels are on the scene, 14 miles west of Fair Isle between Orkney and Shetland. The helicopter was carrying an oil crew change, the coastguard said.
A statement from CHC Helicopter said: "We can confirm that there has been an incident involving one of our aircraft in the North Sea, approximately 32 miles south-west of Shetland. Exact details of the incident, which happened at approximately 3.30pm are not yet known. The appropriate authorities have been informed and the company's incident management team has been mobilised. Further details will be released when more information becomes available."
In May all 14 passengers and crew members on a Super Puma helicopter were rescued after it ditched about 30 miles off the coast of Aberdeen. The helicopter was on a scheduled flight from Aberdeen Airport to a platform in the North Sea at the time.
A year earlier 16 people died when a Super Puma plunged into the sea. Its gearbox failed while carrying the men to Aberdeen. The Bond-operated aircraft was returning from the BP Miller platform when it went down off the Aberdeenshire coast on April 1, 2009.
That incident happened about six weeks after a Bond Super Puma with 18 people on board ditched in the North Sea as it approached a production platform owned by BP. Everyone survived that accident.
A Scottish Government spokesman said: "We are aware that a helicopter has ditched in the North Sea, south of Sumburgh. And we understand that all 19 people on board are now safe and well following the dispatch of emergency services to the site. Scottish ministers are being kept updated on the situation and we will release further information when it becomes known."