An unwanted roller-coaster ride resulted in all passengers on an Air New Zealand flight from Christchurch to Invercargill on Wednesday having their tickets refunded.

Air NZ flight NZ5715 was hit by 180kmh crosswinds during its trip down the east coast.

Passengers were warned it would be a rough ride, but the battering the plane received from air turbulence was almost constant, passenger Owen Scott said.

"It was just about nonstop. We had a 10-minute respite, and then it hit us again.

"But to be fair everything was under control.

"The pilot told us what was going on.

"It was one of those trips which, hopefully, was once in a lifetime," Scott said.

Scott had been in Christchurch with his wife, Cara, who is receiving cancer treatment.

"I was concentrating on her ... but there was no drama - the Air New Zealand people were marvellous."

Another passenger told Stuff about 20 per cent of people on board vomited during the flight.

An Air NZ spokeswoman said the flight made a normal landing, and emergency services were on hand to help some passengers who were feeling unwell.

"Air New Zealand offered customers travelling on the flight a full refund in recognition of their experience, and customers also had the option of attending a debrief with the flight crew," she said.

• Air New Zealand this morning announced it will start its first ever direct scheduled service between Invercargill and Auckland at the end of August.

The airline will operate the direct flight five times a week using its Airbus A320 aircraft.

The airline's head of regional affairs Reuben Levermore says the airline was delighted to get the trial service up and running with the first flight between Auckland and Invercargill scheduled for 25 August.

To coincide with this new route going on sale, Air New Zealand's Grabaseat has today released seats available at $59 one way, with 500 seats available in each direction for travel between August 25 and December 15.

With a flight time of about two hours, the new Invercargill-Auckland service will be the longest domestic Air New Zealand flight.