A typhoon forecast to hit Japan has forced Air New Zealand to cancel flights between Auckland and Tokyo

Flight 99 to Narita International Airport had been due to have departed just after 9am today.

The airline says that as a consequence, the return flight NZ90 from Tokyo to Auckland has also been cancelled.

Air New Zealand said it was continuing to monitor conditions closely.

''In the meantime, customers booked to travel to or from Tokyo (Narita or Haneda Airports) up to and including Friday, 10 August are being offered flexibility.''

Customers are able to defer their travel to another flight up to Wednesday next week in the same class of travel without fare difference or penalty.

On its travel alert page, the airline says that due to the nature of Typhoon Shanshan, Air New Zealand services, as well as onward travel from Tokyo could be further disrupted at any point.

It says it will not be liable for any costs associated with disrupted travel should you choose to travel as planned.

''Any incidental and associated costs such as accommodation and/or meals are not the responsibility of Air New Zealand, and you will need to refer to your travel insurance policy.''

Air New Zealand's next scheduled service to Tokyo is currently scheduled to depart Auckland at 8.55am, Thursday, 9 August.

Flights to Shanghai last week were under typhoon alert and the disruption comes as fallout from Air New Zealand's Dreamliner engine problems continues to hit with some Los Angeles-bound flights cancelled this month.

During August seven return flights have been cancelled and a handful of flights to Nadi from Auckland and Christchurch have been canned over the next three months.

Dozens of flights over the next three months have been rescheduled and different aircraft used on long-haul routes as the airline works to minimise cancellations which have plagued it since last December when Rolls-Royce engine problems came to light.

On its travel alert page this week the airline says re-timed some international flights and made a limited number of cancellations to the end of October due to a global issue requiring earlier than expected maintenance on some of the Trent 1000 engines fitted to its 787-9 aircraft.

''Air New Zealand is doing all it can to minimise the impact of these unforeseen checks on customers and is also working to secure lease aircraft to help with additional capacity.''
It has again warned passengers to call only if essential.

''We anticipate high caller demand for our contact centre over this time and customers are advised to avoid calling unless necessary,'' it said.

The airline's own Boeing 777 aircraft and two leased planes have been put on to routes normally flown by some 787 Dreamliners. Some of the aircraft with the affected Trent 1000 Package C engines have over the last nine months been taken out of service for repairs and there have been restrictions on how far they can fly from the closest diversion airport.

Air New Zealand is leasing Boeing 777s from leasing firm (an ex-Singapore Airlines plane) and from Taiwan's Eva Air.

This has led the airline to warn passengers that due to different cabin configurations there is a chance they will have to travel in a different class.

''We will endeavour to provide a like-for-like seat where possible (including exit row, aisle and window seats). However, where this isn't available, customers will be eligible for a full refund of their pre-paid seating.''

Rolls-Royce is scrambling to fix engines used by Air New Zealand and several other airlines around the world. The engine-maker will take a financial hit of more than $1 billion over the next two years.