The U.K. Civil Aviation Authority will conduct a review of offshore helicopter operations in the North Sea following a fatal accident off the Shetland Islands last month.

Four oil workers died Aug. 23 when a CHC-operated Eurocopter AS332L2 Super Puma ditched into the North Sea just minutes before it was due to land at Sumburgh Airport. Twelve passengers and the two pilots escaped, but one crewmember was seriously injured.

The review, announced a month after the tragedy, will be undertaken jointly by the European Aviation Safety Agency and the Norwegian CAA. They will study current operations, previous incidents and accidents. They will also compare the U.K.’s operations with those in Norway, where statistics show there have been half the number of fatal and non-fatal accidents involving Norwegian operators than among U.K. operators.

The review will be led by the CAA’s head of flight operations, Capt. Bob Jones. He will work closely with Geir Hamre, head of helicopter safety for the Norwegian CAA. They will be supported by a team of experts who will consult with individuals and organizations involved in offshore flying.

The CAA says the final review will also be subject to scrutiny by independent specialists.

The review is the third of its kind to be announced following the Super Puma accident.

The Helicopter Safety Steering Group (HSSG), an offshore safety committee set up following the fatal Bond Offshore Super Puma accident in 2009, requested that the Oil and Gas U.K. trade association for offshore oil and gas companies should also run an independent review of helicopter operations. The HSSG said the review’s terms of reference should be “developed in partnership with all stakeholders, including the trade unions.” Meanwhile, the U.K. Parliament’s Transport Committee announced it would hold an inquiry into helicopter safety and examine whether the government needs to take a more pro-active approach in regulating the industry.

The news was announced as operators and original equipment manufacturers gather in London for the Helitech conference and exhibition, where the North Sea accident remains at the top of the agenda. Operators said they welcomed the news, but several pointed out that the companies already work in one of the toughest and most highly regulated areas of commercial aviation.

“This is an area of aviation where we are audited by the regulators, the oil companies and by the insurers,” said an oil company senior manager. “Major lessons have been learned, and there is now closer cooperation between the operators within the bounds of competition than there has ever been before.”

A group of helicopter operators plan to announce further safety cooperation at the show on Sept. 25.

In the meantime, the AS332L2 has returned to commercial operations after U.K. air accident investigators said they could not find a technical reason for the accident.

Following a nine-month grounding, EC225 operations in the U.K. have yet to fully resume. Eurocopter says that around half of the grounded aircraft have returned to service using interim fixes mandated by EASA in July. But so far only CHC has restarted commercial operations with the type in the North Sea. Bond Offshore said it is working with oil companies before returning the type to flight operations, but won’t say when that will be. Bristow has also taken a similar approach, and managers have previously suggested that a return to operations might not occur until later this year.

The EC225 issues have not halted sales of the aircraft. Bond Offshore’s parent company, Avincis Group, announced it would buy three EC225s for its new subsidiary, Bond Helicopters Australia, to service a multimillion dollar, five-year contract with the PTTEP Australasia Group of Companies in the Timor Sea.

The CAA’s findings are due to be published in early 2014.