While not disclosing what steps it was taking to ensure it won't happen again, the spokeswoman said the issue was specific to the particular aircraft yesterday and the airline was ''confident that it won't cause any issues going forward.''
The plane on Sunday was a five-month-old Boeing 787 Dreamliner, and was the airline's and entered service late last year. Another Dreamliner which took delayed passengers and landed just after midday today was an older aircraft that had flown the route before.
Chinese authorities are sensitive about planes using their airspace, of which large areas can be shut down quickly for military use.
Flight plans are filed around an hour and a half prior to the flight's departure but these were not behind Sunday's problem.
Some passengers on NZ289 complained at the level of compensation for the 24-hour delay.
The spokeswoman said that under the terms of the Montreal Convention, the airline was required to compensate for actual, provable losses incurred as a result of this disruption.
Passengers were provided with accommodation where necessary, and meal vouchers. As a gesture of goodwill each customer also received a $200 voucher to spend on shopping at the airport.
Aviation commentator Irene King said the said it was an administrative ''cock-up'' that shouldn't have happened.
New Zealand rules are different. A Civil Aviation Authority spokesman said once the operator has an international air licence issued by Ministry of Transport, regulatory approval issued by the authority, and has negotiated landing slots with the airport operator then the only thing required on a flight-by-flight basis is a flight plan that is accepted by Airways NZ.
Prime Minister Jacinda Ardern said the mistake was Air New Zealand's and was separate to China-New Zealand relations.
"It is important to be really clear and not confuse administrative and regulatory issues as issues to do with the relationship."
Asked how she could be sure that this had nothing to do with any political reasons, she said: "Aircraft travelling into China are required to be registered. This one was not. That is the issue that has occurred here."
National Party leader Simon Bridges has criticised the Government for its stance towards China, saying it probably played a role in the fact that Ardern was not invited to visit China last year.
Ardern has said the visit didn't happen because of scheduling difficulties.
Since taking office, the Government has criticised China's military buildup in the South China Seas in a formal Defence strategic policy document, and raised doubts over China's Belt and Road Initiative.
It has also welcomed Australia's plans for military engagement and infrastructure spending in the Pacific - a bid to counter China's influence in the region.
China also responded to the decision to rule out Huawei's involvement in Spark's 5G plan by saying that treating Chinese companies with fairness would help bilateral relations.
The Government, which is renegotiating the NZ-China free trade agreement, has said the Huawei decision was not political.
Ardern said she had received an invitation from the Chinese administration to visit China, but dates had yet to be finalised.
Air NZ - which carries around 18 million passengers a year and about 45 international flights a day - has had a turbulent fortnight.
Two Rarotonga flights were cancelled at the weekend. The Air New Zealand spokeswoman said a runway lighting problem on the island as a result of a lightning strike ''impacted'' the airline's ability to operate NZ18 on Saturday.
''NZ19 was also impacted as a consequence,'' she said.
At the end of January it announced an earnings downgrade which showed half-year profits could slide by as much as $185 million on previous estimates. The airline says subdued demand and the impact of Rolls-Royce engine problems would eat into pre-tax earnings.
And last week it copped some flak for its handling of passengers after high winds forced a Queenstown-bound aircraft to divert to Christchurch and then fly on to Auckland.
While one passenger said the situation was handled well, another said people were ''losing their minds'' and were extremely angry. Another complained of being treated like cattle.
Air New Zealand announces its half-year result on February 28.
