LONDON (Reuters) - A British safety group on Thursday ended a six-day suspension of flights by Super Puma helicopters in the North Sea, imposed after four oil rig contractors were killed in a crash last week.
Although the cause of last Friday's fatal accident near Scotland's Shetland Islands remains unknown, the Helicopter Safety Steering Group (HSSG) said there was no evidence to continue a suspension on flights put in place on Saturday.
The grounding of all types of Super Puma helicopters, which make up about half of a 75-strong fleet used to carry workers to and from UK offshore platforms, left North Sea operators trying to find alternative ways of transporting staff and supplies.
HSSG spokesman Les Linklater said several aviation authorities, a pilots' union and helicopter operators themselves had expressed confidence in the aircraft made by Eurocopter, a unit of Europe's top aerospace group EADS.
He said three types of Super Pumas - L, L1 and EC225s - would return immediately to service but the Super Puma L2 model involved in Friday's fatal crash would initially be re-introduced for non-passenger operations only.
"There is no evidence to support a continuation of the temporary suspension of the entire Super Puma fleet," Linklater said in a statement following a two-day meeting.
The crash was the fifth accident in four years in the area involving different models of Super Pumas which included a fatal crash of an L2 in April 2009 in which 16 people were killed.
It came as the helicopter industry tries to rebuild confidence after two EC225 aircraft ditched in the North Sea last year due to gearbox problems and the aircraft was suspended in the area for almost 10 months until July this year.
The North Sea is one of the world's largest oil and gas producing regions with almost 57,000 workers travelling to offshore facilities in the area last year and safety issues are watched closely by regulators worldwide.
Britain's Air Accident Investigation Branch (AAIB) said on Thursday that a search team had found the black box from Friday's crash with flight data and cockpit recordings which would now be examined to try to establish the cause.
The AAIB said the helicopter appeared upright and intact when it entered the water, slowing down before it crashed.
The union Unite said the continued grounding of the L2 fleet was the bare minimum the industry could do until the recovered black box's data fully established what happened.
"Confidence has been shattered and the industry needs to provide substantive evidence - not opinion - to its workers demonstrating the airworthiness of the helicopters that are now returning to operations," Unite Scottish Secretary Pat Rafferty said in statement.
An online petition urging for all Super Pumas to be banned has gained more than 12,000 signatures and a Facebook page called "Destroy The Super Pumas" has 37,500 likes.
Linklater said the accident was a tragedy but there are almost 16,000 people offshore currently, including about 250 people who have spent more than 21 days offshore.
"We have a duty of care to all offshore workers both in terms of their safety and their well-being," he said, adding a sympathetic approach would be taken to workers who did not feel they could fly.
The suspension of Super Puma flights was causing delays and flight backlogs as the rest of the fleet, comprised mainly of U.S. manufactured Sikorsky Aircraft, a unit of United Technologies Corp, tried to meet demands.
But the industry is used to short-term disruptions caused by bad weather and changes schedules to shift non-essential maintenance activity to reduce impact on production.
Spokesmen for France's Total, BP and Royal Dutch Shell said production was not impacted.
Additional reporting by Rhys Jones; Editing by Pravin Char