Audrey Wood, whose son Stuart was one of 16 people who died in April 2009 when a Super Puma ditched into the sea off Scotland, said the bereaved had been assured such an incident would not be repeated.
"The men who are travelling back and forth have to be reassured their safety can be guaranteed. Our heartfelt sympathy goes out to these families, we know what they are going through," she said.
James Costello, 24, was the youngest victim of the 2009 crash which was later found to have been caused by a gearbox failure.
His mother Verona Szegedi from Aberdeen said it was "unacceptable" that lessons had still not been learnt from the tragedy.
No prosecutions resulted from the disaster and a fatal accident inquiry has yet to take place.
"Here we are four-and-a-half years on, and there is another helicopter accident with fatalities," she is reported to have said.
"It is just awful and I cannot see why things have dragged out. An inquiry might help prevent future tragedies but instead there have been long delays. It is not good for anybody; for the families it is agony."
The 2009 crash involved a Super Puma operated by Bond Offshore Helicopters, which was on its way to Aberdeen from BP's Miller oil platform.
The two pilots and 14 oilmen on board were killed when the aircraft ditched 14 miles from the Buchan coast. It was the biggest loss of life in a helicopter accident in the North Sea for 20 years.