A gust of wind, pilot error or mechanical failure could have been to blame for carrying an ill-fated balloon into power lines yesterday, sparking a catastrophic fire and cutting power to 3800 homes.
An expert says long strings of power lines pose significant hazards for many forms of aviation.
Police yesterday confirmed that as a hot air balloon was preparing to land in a Carterton paddock, it was caught in wires on a power line, causing sparking in the basket.
One couple are believed to have jumped from the basket, just before the heat caused the balloon to leap upwards as it was engulfed in flames. It then plunged into a paddock. All 10 passengers and the pilot died.
Balloon Aviation Association president Martyn Stacey said pylons and power lines posed a danger for aviation pilots but there has been no official analysis of the extent of that danger or the frequency of aircraft tangling with the lines.
He said in New Zealand, power line strikes were rare.
"But in the United States, the rate of hitting power lines in any form of aviation is incredibly high.''
Mechanical failure, a pilot error or a sudden gust of wind could have lead to the incident yesterday, Stacey said.
There were also two possible explanations for the sudden, sharp ascent of the balloon.
"With the fire in that balloon it's put heat in, which has made it rise,'' he said. "Or if someone jumps out of the balloon, you've lost more than 100kg of weight and the balloon is going to go racing upwards.''
The Transport Accident and Investigation Commission, CAA, police, the Department of Labour and the Coroner's office are investigating.
