The fatal Super Puma helicopter crash off Shetland was not caused by airworthiness or technical problems, based on current information, the Civil Aviation Authority has said.
Helicopter operators are making arrangements to return their fleets to service after the suspension of flights was lifted.
The CAA said it considered the decision to resume flights as "appropriate".
The flight data recorder is being analysed by investigators.
A CAA spokesman said: "As the UK's aviation safety regulator, protecting the public is our fundamental purpose.
End Quote CAA spokesperson
We would not allow a return to service unless we were satisfied that it was safe to do so"
"It was right that Super Puma operations were suspended in the immediate aftermath of the accident on 23 August, until further information was available.
"We have reviewed and assessed the evidence available, including the information already published by the Air Accident Investigation Branch and detailed information provided to us by the operators.
"Our team of specialists includes pilots who are experienced in flying the Super Puma AS332 L2 in the North Sea environment."
The spokesman added: "Based on all the information currently available, we do not believe that the accident was caused by an airworthiness or technical problem, and consider that the decision by the operators to resume Super Puma flights is appropriate.
"We would not allow a return to service unless we were satisfied that it was safe to do so. We will review the position if any new evidence comes to light."'Duty of care'
None of the three North Sea helicopter operators had Super Puma passenger flights on Friday.
The Helicopter Safety Steering Group (HSSG) said a campaign to engage with the offshore workforce was under way.
Les Linklater of HSSG said: "Four people tragically lost their lives on Friday. However there are almost 16,000 people offshore currently, with over 12,000 in the most affected areas (central and northern North Sea).
"Today, there are over 250 people who have spent more than 21 days offshore, this is increasing daily and they and their families are wondering when they are going to get home.
"We have a duty of care to all offshore workers both in terms of their safety and their well-being; we must consider the cumulative risk of the 'time out'. We must avoid a further tragedy through the introduction of human factor-based risk such as fatigue, stress and other well-being concerns that increase the likelihood of a high consequence - low frequency event."
He added: "The individual helicopter operating companies will now work with their customers, to ensure the correct information and confidence-building communication is available, sensitive to the individual needs of the offshore workforce, before returning to full commercial passenger service."
Bob Crow, general secretary of the RMT transport union, told BBC Scotland's Good Morning Scotland programme that he backed the decision to return the Super Pumas to service, in light of the evidence currently available.
He said: "You've got to weigh up, at the end of the day, the pressures on individuals who are stranded on rigs and want to get back, or who've been away from work for two to three weeks.
"Also, at the end of the day, we've got to look at the evidence that was put in front of us and at this moment in time there's no reason why the crash was mechanical."'Back of my mind'
One offshore worker told BBC Scotland: "I am slightly concerned about how fast they are back out."
Another said: "Obviously there is a bit of concern because of what's been happening over the last couple of years, but basically (I will) try and put it to the back of my mind and just do what we are here to do."
The Air Accidents Investigation Branch (AAIB) said the Super Puma had appeared to show a "reduction in airspeed accompanied by an increased rate of descent".
The AAIB said it appeared the helicopter had been intact and upright when it entered the water.
Four people died when the Super Puma AS332 L2 went down close to shore on a flight to Shetland's Sumburgh Airport from the Borgsten Dolphin rig.
They were Duncan Munro, 46, from Bishop Auckland, Sarah Darnley, 45, from Elgin, Gary McCrossan, 59, from Inverness, and George Allison, 57, from Winchester.
The crash was the fifth incident involving Super Pumas in the North Sea since 2009.
Aberdeen North MP Frank Doran has called for a public inquiry.