The younger brother of the heir to a multimillion dollar property empire has told of watching his "talented" older sibling crash and die in his private plane.

Stacey Hopper, 27, was killed instantly when the family aircraft he was piloting crashed into an occupied van at the Marsden Cove Marina, south east of Whangarei on Friday.

His younger brother Gray Hopper, 24, said high winds caught the Cessna 206 as it took off from the temporary airstrip, causing it to clip the Volkswagen with one wing, before crashing into the field.

Family friend and business partner Simon Fitzpatrick was in the van with his 10-year-old son at the time. Neither suffered serious injuries.

Stacey, known to family and friends as Stace, is the oldest son of Leigh and Gwen Hopper of Hopper Developments, the company responsible for huge residential coastal developments around the Coromandel Peninsula.

Gray said his brother had flown to the marina from his home in Orewa on Friday to oversee the family's latest building project.

He was watching his brother from the other side of the airfield as the tragedy unfolded. As soon as the plane hit the van, he began running towards the scene.

"It was very windy ... the wind took the plane to one side and as it came down one wing collided with the van and clipped it.

"Simon was first on the scene and I was right behind him, but by the time we got over there the plane was engulfed in flames."

The Civil Aviation Authority and Department of Labour have started separate inquiries, the latter because the airstrip was within the marina's boundary.

Gray said his older brother was outgoing and a "very skilled" flyer, who gained his private pilot's licence four years ago. He and Stace had been flying with their father since they were children.

The Hoppers are best known for their residential work in the Pauanui and Whitianga waterways - among New Zealand's largest coastal land developments. The family were estimated to be worth $120 million by the National Business Review in 2008.

Three years ago, Stace was made project manager for the Marsden Cove Marina development as part of a five-year plan that would see him take over the business from his father.

The marina project involves about 770 houses, each of which will have a private jetty so owners can moor their boats at the foot of their garden.

About 80 plots have been sold and the development is in its second stage, which includes marketing 10 three-bedroom villas and 50 two or four-bedroom apartments for pre-sales.

Gray said as well as flying, Stace also loved jetski stunts and rally driving and often entered the Targa Rally Series in his highly modified Subaru WRX.

"He really had all the skill in the world," said Gray.

"He got his private pilot licence, he's a rally driver and also loved his jetski. He was so competitive. You name it, he could do it.

"It's a pure waste of pure talent. He was very talented and it's a huge loss for society and for our family.

"He was very focused and very mature and was looking forward to [taking over the business]. He took things head-on and didn't know how to fail."

Gray said the family and Stace's girlfriend, Gracie Murphy, were struggling with their loss.

They were gathered at the Hoppers' $1.7 million mansion in Orewa, north of Auckland, yesterday.

"I'm pretty sure you can imagine what they're going through," said Gray. "They've lost their eldest son. We'll try to get Stace back from Whangarei soon and bring him home. That will be good."

He said the family had not yet made funeral arrangements.

Inspector Chris Scahill of Whangarei Police said initial indications were that wind was a factor in the crash, but they wouldn't know for certain until the Civil Aviation Authority investigation was completed.

He said the runway Stace used for take-off was a temporary airstrip and not concreted.

Civil Aviation Authority communications manager Bill Sommer said investigators were at the scene all day yesterday and would look at "everything" in relation to the incident.

"This would include the pilot's background, his training, how he was on the day, the weather, the condition of the airstrip and the condition of the plane and its history."

"Until that has all been looked at we keep an open mind about the incident to make sure there are no preconceived ideas."

- Rebecca Lewis
* Pilots can land and take off from private land in New Zealand at their discretion.
* They must consider visibility, wind and other safety factors.
* While there are 121 official aerodromes, pilots also use up to 500 unregistered airstrips which can be nothing more than a bulldozed dirt track.
* There have been 56 fatal crashes in New Zealand in the past decade and four in the past year.
* The last death was a pilot who crashed his glider south of Blenheim on December 18, 2009.
* The Civil Aviation Authority has records of 7424 aircraft in New Zealand, including planes, helicopters, gyroplanes, gliders and balloons.
* There are 1935 registered planes - including everything from 747s to light aircraft.
* There are about 22,000 valid pilot licenses for all aircraft, including 9979 licenses held for pilots who are only qualified to fly non-commercially.

- Sean Gillespie