About 100,000 people will be affected as Air New Zealand cuts flights from its schedule because of staff sickness.
The airline will operate a reduced schedule over the next six months.
There will be changes to some flights, where there will be 1.5 percent fewer seats than originally planned.
For domestic travellers whose flights are shifted, they will most likely be transferred to another one on the same day, and for international travellers, it will likely be either the same day or plus or minus a day from their original booking.
If travellers' flights could not be rearranged within these timeframes, customers could change their booking online, opt into credit or request a refund, the airline said.
If you have booked through a travel agent, you will need to contact them if changes are needed, or to request a refund if eligible.
It had been a challenging five weeks, with sickness and bad weather having a big impact on the airline, chief executive Greg Foran told Morning Report.
"We really want to avoid getting ourselves into a situation, particularly around Christmas time, of not being able to get people where they need to get to," Foran said.
While domestic travellers will be refunded if the are unable to travel on the same day, Foran said someone whose original flight was in the morning could not get a refund if, for example, they are rescheduled for an evening flight on the same day.
Those with further onward connections may also be disrupted and Air NZ said it would be working directly with impacted customers.
The airline had ramped up call centre staffing to be able to assist with some of the connections and wait times had come down, he said.
Foran earlier said in a statement that by reducing the number of flights, the airline would be able to have crew on standby to cover illness, which had not been possible lately.
This announcement would help give customers a heads up to manage their travel plans accordingly, he said.
"Looking at the disruptions our customers and staff have faced over the past five weeks, we've made some adjustments to reduce short notice cancellations in the months ahead."
Crew sickness rates had been the highest in over a decade and they were stretched to capacity, Foran said.
"We see those challenges continuing not just for crew, but for our whole operation, so are making proactive changes to address them."
More than 2000 pilots, airport staff, cabin crew, engineers had been rehired or employed, he said.
"We're also exploring options to lease a crewed widebody aircraft for the busy summer period."
Air New Zealand plans to be operating at 90 percent of pre-Covid capacity for the next six months in its domestic and international schedules.
Foran said over the past two and a half years in his role he had learnt to "always be ready for the next side swipe in aviation".
"[It's] very hard to predict what's going to happen with Covid, very hard to predict sickness rates overall, but what we can do and are doing is building some more insurance in so that I have more confidence with these actions by just tweaking the system a bit here, then I would if we didn't tweak the system."
Last month, the culmination of school holidays and winter illness caused travel disruptions across the country.