The national carrier has already had more than 4000 staff leave since Covid-19 restrictions took hold in March.
Among these are around 900 mid-to-long-haul crew.
An email sent to staff said the airline had 385 more cabin crew than there currently was work for.
Air New Zealand chief operating officer Carrie Hurihanganui confirmed the plan, saying it was in response to the decline in demand on North American routes.
"We have reduced our Los Angeles flights from daily to three return flights per week, and converted all of our San Francisco flights to cargo-only services," she said.
"We recognise that a reduced schedule will require a smaller number of cabin crew going forward and we are working through what this means for the team."
Redundancies were a "last resort" and any decision would be made in consultation with staff and unions.
"We appreciate that our cabin crew have already made significant sacrifices throughout Covid-19, but sadly our international schedule remains largely limited by border restrictions and unfortunately there is not enough flying to provide sustainable rosters for the number of crew we have," Hurihanganui said.
Union E tū has hit out at the decision, calling on the airline to halt outsourcing.
E tū head of aviation, Savage, said there was no operational reason for Air New Zealand to retain a crew base in Shanghai.
"When the work comes back, it needs to come back to Auckland-based cabin crew.
"For the company to focus on immediate labour costs, without taking into account the bigger picture, is short-sighted and damaging to all aviation workers."
Savage said the airline and the jobs it provides are a vital piece of New Zealand's infrastructure.
An E tū member who wanted to remain anonymous said the proposal was "devastating" for crew.
"Every time as cabin crew, we think we are going to get a reprieve and get back to doing what we love – we keep getting hit down.
"We've already lost 900 mid-to-long-haul crew. We want to see Air New Zealand flourish and we want to save New Zealand jobs. Our goal is to see the airline bounce back as quickly as it can, so we can start getting our colleagues back."
Air New Zealand reported an underlying loss of $87 million for the 2020 financial year, compared to earnings of $387 million last year.
Covid-19 has wiped out its first-half result and statutory losses before taxation, which include $541 million of other significant items, were $628m, compared to earnings of $382 million last year.
The after-tax loss was $454m.
