The Transport Accident Investigation Commission (TAIC) is calling for significant reform of alcohol and drug regulation in the transport industry, including random testing, after a balloon tragedy in Carterton.
The commission released its final report on Thursday, saying the use of cannabis by pilot Lance Hopping may have led to errors of judgement, culminating in the fire and crash that killed 11 people in Wairarapa in January last year.
The commission says the accident was caused by pilot error, with several crucial mistakes by the 53-year-old. Chief commissioner John Marshall says Mr Hopping was a long-term and recent user of the drug.
"The expert toxicologist engaged by the commission advised that the level of two micrograms per litre of THC, which was found in the pilot's blood sample, strongly suggested recent use of cannabis on the morning of the accident," he says.
The investigation found that Mr Hopping let the balloon get below the level of power lines, and then tried to climb above them when a collision was unavoidable, instead of making an emergency descent to give passengers a chance of survival.
The commission says Mr Hopping was not averse to flouting the rules, as he had continued to operate his commercial balloon venture despite his medical certificate expiring six weeks previously.
It says it is well known that cannabis causes cognitive impairment and it is recommending random alcohol and drug testing throughout the aviation, maritime and rail transport sectors.
The commission found no maintenance issues or mechanical defects with the balloon that contributed to the accident.
The tragedy rates as the worst single aviation accident since the Mt Erebus DC10 crash in 1979.
Pilot investigated in 2010
The Transport Accident Investigation Commission's (TAIC) report reveals that Lance Hopping was investigated by the Civil Aviation Authority over a complaint that a flight was cancelled because he was too drunk or too high in February 2010.
However, the authority's chief executive, Graeme Harris, says staff were unable to substantiate the claims and the issue was not taken further. He says the investigation was potentially a missed opportunity.
"With the benefit of 20-20 hindsight and the evidence of the TAIC recommendation, it would've been an ideal opportunity to prevent this absolute tragedy.
"But I guess the staff of the CAA need to act lawfully, they need to act within the scope of their powers and they can't go beyond them."
The commission says the documentation of what was done was inadequate and if the CAA had taken a more prompt and coordinated response, it could have identified a potential safety risk and a range of preventive actions.
Victims' families call for mandatory drug testing
Relatives of victims of the tragedy have called for mandatory drug tests in the transport and adventure tourism industries.
Sheryl Rule, whose aunt and cousin died, says cannabis use by people who hold other's lives in their hands should be everyone's concern.
Allan Still, father of 19-year-old victim Alexis Still, says he would like to see law changed to enforce mandatory random drug testing in adventure tourism.
"What we would like to see as a family, and I guess it needs the will of the lawmakers - and that's the politicians and the officials - they have to kind of make a stand for not only the victims of the Carterton balloon, but for all New Zealanders and foreign tourists who are going to use ballooning or any other adventure tourism."
Transport Minister Gerry Brownlee says he will await advice from the Ministry of Transport on whether legislative change is needed on the commission's recommendations. He expects to report any proposals to the Cabinet early in 2014.