Helicopters affected by the largest grounding in New Zealand aviation history following a fatal accident have been cleared to fly again.
On Saturday, the Civil Aviation Authority ordered all people operating Robinson R44 machines fitted with a C016-7 'Dash 7' main rotor blade to stop flying the choppers.
This followed the deadly accident in Otago's Lochy River basin last Thursday.
Wanaka resident Stephen Anthony Nicholson Combe, 42, and James Louis Patterson Gardner, an 18-year-old from Queenstown, were killed in the accident.
Both men worked for Queenstown helicopter company Over the Top.
After the crash, sections of the helicopter's main rotor blade were sent to Wellington for laboratory testing.
Investigators have now determined the Dash 7 rotor was not to blame for the crash.
"The blade retrieved from the Lochy River had failed due to overloading - probably due to impact damage," Civil Aviation director Graeme Harris said.
"It was highly likely that it was damaged during the accident sequence rather than being the failure that initiated the accident," he added.
"Now that we have established that the blade failure in the Lochy River basin was the consequence of the accident rather than its cause, I am satisfied the precautionary grounding of aircraft with the Dash 7 blade can be safely removed."
Today's announcement will be welcome news for New Zealand operators whose aircraft were grounded. This week, operators had raised concerns about an uncertain wait and the possibility of financial losses.
The grounding affected 80 aircraft - the largest in New Zealand aviation history.
The R44 is among the most common helicopters in the world and is widely used in New Zealand's agriculture and tourism industries.
Robinson R44s are light, four-seater helicopters capable of achieving a top cruising speed of about 217km/h.