The airline, the New Zealand government and Chinese authorities have all said it was due to an administrative issue.
In a statement Air New Zealand said the plane was new to the company's fleet, and did not have the correct paperwork allowing it to land in China.
New Zealand's Prime Minister Jacinda Ardern smiles as she attends the World Economic Forum (WEF) annual meeting in Davos, Switzerland, January 22, 2019.
An Air New Zealand plane forced to turn around en route to Shanghai did so for diplomatic reasons, but not because of recent unease with New Zealand's relationship with China. "In this case they were using a temporary plane which wasn't registered, hence the effect", the prime minister explained.
"I've just experienced a new level of China Bad: midway through our flight from Auckland to Shanghai, the pilot informs us that Chinese authorities had not given this plane permission to land, so we needed to turn around".
NYU Shanghai assistant professor Eric Hundman was on the diverted flight and tweeted about the experience.
Hundman said Air NZ also offered passengers a "gesture of goodwill" in the form of a voucher worth 200 USA dollars, in addition to paying for hotel rooms.
"We know customers will be deeply disappointed and frustrated by this situation and we are very sorry for the disruption to their travel plans", the airline said.
The death on the Air New Zealand flight comes close to two months after a passenger also died on a Samoa Airways flight from Auckland to Samoa.
Scheduling clashes happen - we all have to postpone sometimes.
The incident has created a potential headache for New Zealand's government, which has recently suffered frosty relations with Beijing.
Dismissing such conjectures as "irresponsible", Ardern accused the opposition of spreading "misinformation".
An opening ceremony event was to be held at Te Papa on February 20, coinciding with the hosting of 2,300-year-old Chinese artefacts, the Terracotta Warriors: Guardians of Immortality exhibition.
"In the past New Zealand has enjoyed a consensus approach to foreign policy, a unified front, that's in New Zealand's best interests".
This was a plane flying in the middle of the night, on weekend, to a country which only a few years ago blocked all meat imports from New Zealand for more than a week because the Ministry of Agriculture and Fisheries had been rebranded the Ministry for Primary Industries, meaning export paperwork changed slightly. "That was a effect", she added.
The prime minister asserted that despite complexities in ties, Auckland's relationship remains robust. "Is it part of the ongoing deterioration in relations between this NZ Govt & China?" The exhibition runs until April 22, 2019.
"Look, I have received an invitation from the Chinese administration to visit", she said Monday.