Onboard "haze" forced Air New Zealand flight to make a hasty landing at Nelson Airport this afternoon.
Flight NZ5038 took off from Christchurch and was bound for Hamilton when it had to make an unscheduled landing about 3pm.
Emergency services were at the scene.
"All we were told was that there was 58 passengers on board and it was landing here and there was a problem with smoke in the cockpit," Nelson Fire senior station officer Steve Shackleton said.
Passenger photographer Dianne Manson confirmed there was a haze inside the plane.
"You could smell it. It smelled like kind of a burning rubber, electrical burning and a couple of passengers asked the air hostess what was going on."
The cabin crew spoke to the pilot and then came back and kept the passengers informed, Mrs Manson said.
"Everyone was quite calm. They told us straight away what was happening."
After they'd landed, the captain told them it was an electrical fault.
"They were really good about it," Mrs Manson said.
She was due to arrive in Hamilton about 4pm, but would now get there three hours later after flying to Wellington and then to Waikato, where tomorrow she will photograph the cycling track nationals.
A fire engine from Nelson was at the airport on standby, and an airport fire appliance also attended.
An electrical fault was believed responsible for the haze, Mr Shackleton said.
"We were there to assist. I don't think it was too much of a problem."All passengers are now off the plane.
An Air NZ spokeswoman said the landing was a "precautionary measure due to a haze being detected onboard".
"The aircraft landed in Nelson without incident at 3.15pm. Engineers are inspecting the aircraft and customers will be re-accommodated," she said.