A Rotorua coroner's hearing into a plane crash that killed two Australians and the pilot has heard every second plane flying into Taupo Airport with a certain type of navigational equipment is "pulled" off course towards Mt Tauhara.
Dr Wallace Bain heard this from lawyer Philip Grace, who is acting for the family of pilot Steve Brown, who crashed into the mountain killing himself and two prominent Australian socialites, Christine and Bernie Lewis.
The couple and the pilot, from Christian Aviation, died after the light plane slammed into the mountain about 11.30am on February 2, 2005. They had been heading to Taupo from Kerikeri after they couldn't land because of bad weather.
Mr Grace told the court the accident could have been avoided had the Civil Aviation Authority (CAA) been told of two incidents in October 2001, when two Air New Zealand planes were "pulled" off course towards the mountain.
He said a report on the incident by Airways, New Zealand's air navigation service, explained one of the planes carrying 17 people avoided crashing only because cloud lifted giving pilots a view of the mountain.
The trio would still be alive today had other pilots been warned of the problem, he said.
The Airways report indicated this was happening to 50 per cent of planes heading into Taupo using an Aircraft Direction Finder (ADF).
ADF is used by pilots as there are no air traffic controllers at Taupo Airport to direct pilots. The equipment could give false readings depending on the weather at the time, the court heard.
Mr Grace said, in evidence, it was "extraordinary" no one had passed on information to the CAA to warn other pilots of the problem.
The issue had been filed away as it had been identified the problem could be resolved once GPS was introduced for flying into Taupo, he said.
Mr Brown's plane had GPS fitted but he wasn't certified to use it.
"It was filed in the too-hard basket ... they decided to do nothing about it," he said.
"It just beggars belief this has happened ... every second plane flying into Taupo could crash into Mt Tauhara."
Within a month of the deaths, Air New Zealand stopped flying into Taupo, Mr Grace told the court.
"The general public were told nothing," he said.
"Airways has known this has been an ongoing problem for about 10 years."
Meanwhile, Mr Lewis' son, Mark Lewis, who has been an RAF pilot and is a private pilot, made several submissions about the same issue as well as on Mr Brown's health.
He, his sister Vanessa Willans and uncle, Lawrie Lewis, flew to New Zealand for the inquest to find "clarity".
An autopsy discovered the pilot had disease around a replaced heart valve and 14 grams of carboxy-tetrahydrocannabinol in his blood - showing he had possibly had cannabis in the 48 hours before his death.
Mr Lewis also claims baggage wasn't secured in the plane - which breached aviation rules.
Mr Brown's family denied he had ever used drugs, stating he was anti-drugs.
Mr Lewis said the "culture" regarding medical testing for pilots needed to be upgraded and regulations needed to be brought up to world standards.
Outside New Zealand, pilots with heart problems are not able to fly alone, the court heard.
Safety needed to be paramount, Mr Lewis said.
"It's disappointing we have an environment in New Zealand that is like this ... safety needs to be placed about economics," he said.
Meanwhile, his family have been left gutted by the deaths of their "precious" family members.
Mr Lewis wears his father's wedding ring on a chain around his neck, while his sister wears her mother's gold earring and ring she was wearing at the time of her death.
Today the brother and sister run the mortgage finance company their parents started which Mr Lewis said was helping them deal with their grief.
"Obviously, there is grief and sadness.
"We have tried to deal with it as best we can and the wonderful legacy they have left," he said.
Meanwhile, Dr Bain adjourned the inquest to get more information regarding Mr Brown's medical condition.
"It's a complicated case," he said.