LONDON (AP) — Britain's Civil Aviation Authority is calling in international experts to help improve the safety of helicopter operations in the North Sea after a string of accidents, including an August crash that killed four people.

The CAA said Tuesday it would conduct a review along with its Norwegian counterpart, the European Aviation Safety Agency and independent experts.

There have been five accidents in the past four years involving helicopters used to ferry workers to and from oil platforms off the Scottish coast. One crash, in April 2009, killed 16 people aboard a Super Puma helicopter.

The review will look at issues including airworthiness and pilot training, and will compare British operations with those in Norway, which has a large offshore oil industry.

The findings are due to be published next year.