Unite Scottish Secretary Pat Rafferty insisted the Super Puma fleet of helicopters must remain grounded while workers' confidence remained "shattered":
The continued grounding of the L2 fleet - the same type involved in last Friday's crash resulting in four fatalities and also in the April 2009 crash with 16 fatalities - is the bare minimum that the industry can do until the recovered black box's data fully establishes why this tragedy occurred.
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.
At the same time, Unite is demanding guarantees from employers that workers who feel unable to fly will not be subject to pressure or the threat of dismissal.
The industry cannot merely expect the workforce to simply get their boots on and get back to work.
The Helicopter Safety Steering Group said the decision was based on confidence from a group of five unions and organisations after five days of safety reviews.
Les Linklater, Step Change in Safety's team leader, said: “We have had the opportunity to review key elements of our fleet and better understand the positions of the authorities that determine the airworthiness and operational compliance and safety of our helicopter fleet.
"The result is that there is no evidence to support a continuation of the temporary suspension of the entire Super Puma fleet."
CHC has temporarily suspended all flights of the three types of Super Puma helicopter that it operates - the L, L2 and EC225 following the fatal crash off the coast of Shetland.
Fellow operators Bond Offshore Helicopters and Bristow also enforced a temporary suspension of all Super Puma flights except emergency rescue missions, in the wake of a recommendation by the industry's Helicopter Safety Steering Group.
The freeze on using the helicopter type is causing disruption to the movement of workers both on and off shore.
Four oil workers were killed when a Super Puma AS332 L2 travelling from the Borgsten Dolphin support vessel came down off the southern tip of Shetland last week with 16 passengers and two crew on board.