Billionaire businessman Michael Erceg flew his executive helicopter - and the Dutch businessman who was his passenger - into treetops that he apparently failed to see in time, according to a Civil Aviation Authority (CAA) report released today.

Both Mr Erceg and Guus Klatte, 38 - the export director of Dutch brewer Grolsch - died in the crash on November 4, 2005, 11km southwest of Raglan. A coroner's inquiry into the two deaths was today under way in Hamilton.

Mr Erceg's personal wealth was estimated at $1.25 billion when his company, Independent Liquor, was sold after his death.

His wife Lynette and brother Ivan ensured millions of dollars were spent on the search for the Eurocopter and the family was reported to have fought the official findings of the CAA investigation for two years.

Mr Erceg had wanted to personally show Mr Klatte New Zealand from the air by flying to Queenstown from Auckland.

But though the liquor baron gained his helicopter licence two years earlier, had logged 237 hours and had recorded most of the 155 hours in the Eurocopter as "pilot-in-command", he actually often flew with an accompanying instructor as a safety pilot.

Mr Erceg did not hold an instrument rating for flying in cloud and mist, without visibility.

Today the CAA report said Mr Erceg "probably did not appreciate the significance of the forecast deteriorating weather" and flew at nearly 170km/h towards rising ground, low cloud and decreasing visibility.

In his last minutes, he was left with few alternatives.

Mr Erceg had limited first-hand experience in extended cross-country flight and weather decision-making and kept on flying into the deteriorating weather, possibly losing all visibility in mist and then losing control of the helicopter, the report said.

Or he may have lost control while trying to turn away from the high ground and low cloud: the helicopter appeared to have turned back from its route just before crashing in a small grove of trees in a valley of open farmland.

The tail rotor was below the body of the helicopter, which had its nose tipped up 10 degrees, when it clipped tree branches and broke off. The helicopter then began a death-spin, hitting trees with such force the fuselage was cut in half.

The rear passenger seats were relatively undamaged, but the two businessmen in the front suffered unsurvivable injuries in the high-speed impact.

Mr Erceg failed to activate his flight plan, but at Raglan turned inland, apparently to head for Wanganui, where he wanted to refuel, despite the Te Kuiti area forecast he obtained shortly before take-off warning of visibility reducing to 1500m in mist.

A nearby farmer said that at the time there was low cloud rolling with some speed over the mountain's 274m ridgeline.

The aircraft was not found until November 19, after a reported $8m had been spent on searching, when broken branches on the trees he hit started browning off. The aerial on the helicopter's locator beacon broke, so none of the 3000 emergency messages it sent were picked up.

- NZPA