Air New Zealand's 40-minute flight between Christchurch and Nelson had transformed into a 25-hour bus ride when the airline was forced to cancel several flights due to bad weather. Passengers had no choice but to spend the night on board three buses.

Roads were impassable with slips. One bus was forced to stop at Kaikoura and find accommodation at 1 am. One of the passengers in the bus was Rachel Thomas who said the bus driver had "ignored" obvious signs that they could not go through the road.

She said the bus had to drive on the other side of the road and around bends because there was surface flooding. Thomas could see lots of cars pull over with their roofs up.

Sarah Williams, Regional Airlines general manager, said Air New Zealand will be under investigation to determine if it did anything wrong. She said the 25-hour trip was "rather exhausting" for people and passengers should not have experienced it.

Thomas said it was never their intention to put their customers through a "long and daunting journey." Since the incident, Air New Zealand passengers were refunded for their tickets and received $250 as compensation.

Bomb threat forces Air NZ plane to turn back

Meanwhile, a passenger from an Air New Zealand flight to Napier spoke to Hawke's Bay Today about an incident in which the plane was forced to return to Auckland on May 1 after a bomb threat. The 15-year-old teen who asked the paper not to be named, said there were 40 passengers aboard and knew nothing about why the plane made the sharp turn.

She said the plane was about half an hour into the flight when she heard cabin crew announce that they were turning back to Auckland. The teen passenger said the air crew member was looking "distressed" and she noticed the plane was flying low than usual.

It was not until the plane landed in Auckland airport that passengers were informed about the threat. When the plane landed, passengers were told to grab their luggage and move out of the plane quickly.

She thought the plane was going to explode. She thought one of the crew or the captain said a bomb threat was made. The teen left her passport in a hurry but she was thankful someone had grabbed it on the way out.

According to spokesperson for Air New Zealand, a woman who arrived late at the airport for the same flight had reportedly made a "non-specific verbal threat involving the flight" to ground staff. Officials said the plane was already in the air when the threat was made so it was requested to head back to Auckland as a safety precaution.

Aviation security checked the plane thoroughly after it was vacated and found no evidence of a bomb. A woman, 57, was arrested by police and charged under the Civil Aviation Act for communicating false information.