Flight data shows air traffic has dropped 85 percent in the past seven days, compared with the same week last year.
Airways New Zealand which is the country's air navigation service provider, said the number of flights had gone from 6600 to just 982.
Under normal circumstances, New Zealand would expect 703 international flight arrivals every week through March. In the week to 28 March, there were 304 across the country.
In the past seven days, just 50 international passenger flights have landed in New Zealand.
Airways said domestic air traffic halved immediately following the lockdown announcement, down from about 8600 flights weekly to 4400.
The suspension of domestic Jetstar and Air New Zealand services means 95 percent of domestic passenger flights have now stopped. The remaining aircraft still operating domestically are mostly freight and medical flights.
"It is true that we are operating in an aviation environment unlike anything seen since the Second World War," Airways chief executive Graeme Sumner said.
"In December 2019, there were 25 international carriers operating in New Zealand and now there is effectively one."
Domestic travel was forecast to recover at a modest pace after the lockdown and for the rest of the year.
However, Airways warned that international air traffic would take up to two years to recover.
The collapse in air traffic levels has meant Airways was now looking to reduce its costs by 30 percent, including making about a quarter of its staff redundant - about 180 people.
Sumner said Airways was consulting with its staff, unions, the Civil Aviation Authority and airlines.
That process was expected to take some months.
The government's aviation support package announced last month included a $70 million equity injection for Airways.
"While we are greatly appreciative, and this package has made a significant contribution to cushioning the blow, it cannot realistically offset the 95 per cent decline in revenue we are currently facing," Sumner said.