The parents of four tourists who died in a 2010 plane crash have written to New Zealand’s Prime Minister urging him to improve safety measures for adventure sports in the country.

Prime Minister John Key’s office confirmed Monday that the families wrote following the release of a coroner’s report into the skydiving plane crash that killed nine people. The families from England, Ireland, Germany and Australia said New Zealand needs to take action to assure tourists it’s a safe place.

Key’s office had no immediate response. Last year, spokesman Kevin Taylor said “visitors to New Zealand can be assured that we take safety extremely seriously.”

Coroner Richard McElrea’s report concluded the small Walter Fletcher plane operated by Skydive New Zealand was overloaded and the weight incorrectly balanced when it crashed soon after takeoff near Fox Glacier. McElrea found there was likely another factor such as pilot error which contributed to the crash, adding the exact cause may never be known.

The coroner recommended the industry urgently review making it mandatory for skydivers to wear safety belts on takeoff and that small planes like the Walter Fletcher be restricted to six passengers.

The families said they lack confidence in the ability of New Zealand’s Civil Aviation Authority to regulate safety aboard small planes and they believe the country needs to introduce new laws to allow bad operators to be sued for negligence, something which is difficult or impossible under existing laws.

“We know you are aware of the indescribable grief and anguish the loss of our loved ones has caused us,” the families wrote. “It is only now that we have all been able to come together in this way.”

Adventure-tourism plays a significant role in New Zealand’s economy. About 2.6 million tourists visit each year, according to government statistics, with about one-third participating in sports such as bungy jumping, skydiving or jet-boating.

Opposition lawmaker Andrew Little said the country needs a more robust culture of risk assessment.

“The families are correct when they say New Zealand is too blasé about health and safety, and this accident was yet another wake-up call to do better,” Little wrote in a release Monday.

The tourists who died were Glenn Bourke, of Australia; Patrick Byrne, of Ireland; Bradley Coker, of England; and Annika Kirsten, of Germany. The others who died were New Zealand pilot Chaminda Senadhira and tandem skydiving instructors Michael Suter, Rodney Miller, Christopher McDonald and Adam Bennett.

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Photo Credit: Tandem skydiving in action in New Zealand. Heath Powell / Flickr