Air New Zealand will operate a reduced schedule over the next six months as staff sickness levels continue to cause disruption to travel.

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.

Air New Zealand said those with further onward connections may also be disrupted and they would be working directly with impacted customers.

In a statement, chief executive Greg Foran said 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.

Last month, the culmination of school holidays and winter illness caused travel disruptions across the country.