An aviation expert says Air New Zealand is not to blame for its cancelled flights.

Issues with Rolls-Royce engines on its Boeing 787-9 [seven eight seven nine] aircraft mean flights to Perth, Sydney and Tonga between December 10 and January 5 face changes.

Geoff Thomas says [told Heather du Plessis-Allan] it's solely a Rolls-Royce problem - which has been ongoing for three years.

He says Air New Zealand isn't the only airline affected by the engine issues.

"Half the world's 787s, and there's about 900 flying around the globe at the moment, half of them are powered by Rolls Royce engines." 

The union for Air New Zealand's cabin crew says it's doing everything to prevent staff redundancies.

The airline announced cancellations to numerous international flights during the holiday season.

Issues with Boeing 787-9 [seven eight seven nine] engines mean the carrier's changing flights to Perth, Sydney and Tonga - between December 10 and January 5.

The union's aviation head Savage says the airline can lease aircrafts and engines, so crew can keep working.

But he says there might not be enough options, which would leave employees out of work.