The number of Air New Zealand international passengers affected by Rolls-Royce engine problems on the airline's Dreamliner fleet has grown to about 9000 this week.

The airline has cancelled or rescheduled scores of flights because of checks on engines and range restrictions for the aircraft.

When the scale of the problem emerged last week Air New Zealand said 6500 passengers would be affected over a week.

Today it said the impact was confined to two key United States routes (Los Angeles and Houston) as well as Japan services operating to and from Haneda airport and a limited number of transtasman and Pacific Island flights. On its website, it says flights to Perth from Auckland and Christchurch have been hit by a wave of cancellations.

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Air New Zealand said the number of customers likely to be affected by these changes is less than three percent of all passengers travelling with it this week.

It has also explained why some of its Dreamliners are making new refuelling stops.

Chief operational integrity and standards officer David Morgan said depending on weather conditions, some flights may not be able to depart with all the fuel they need, prompting fuel stops. During the weekend, 787-9 flights made fuel stops at Sydney, Cairns, Darwin and Guam.

"Having the flexibility to make a short fuel stop means we are more likely to be able to take a full contingent of customers and cargo,'' he said.

''The alternative would see us potentially having to disappoint significant numbers of customers by moving them to later flights. We are committed to doing everything possible to avoid this, particularly during this busy school holiday travel period.''

Air New Zealand has cancelled or rescheduled scores of flights because of checks on engines and range restrictions for the aircraft. Picture / Peter Meecham
Air New Zealand has cancelled or rescheduled scores of flights because of checks on engines and range restrictions for the aircraft. Picture / Peter Meecham

The fuel stops take about an hour to complete and passengers must remain on board. Where possible the operating pilots will increase speed to make up time to achieve an arrival time at destination as close to schedule as possible.

Passengers who have a connecting flight booked on the same ticket, and who are likely to miss it as a result of the fuel stop, will be re-booked onto the next available connection.

A US Federal Aviation Administration airworthiness directive reduces the time Boeing 787-9 aircraft with a specific model of TRENT 1000 engine can be away from a diversion airport from more than five hours to 140 minutes.

The FAA has warned of the of risks compressor blades could crack with vibration in the engine and could result in twin engine failure. Two Air New Zealand Dreamliners have been grounded while engines are repaired in Singapore.

Rolls-Royce senior VP of civil aerospace Ewen McDonald said the company was working towards a permanent fix.

''To completely eliminate this problem we are working on a new type of blade which will remove the need for repeat inspections. The first of these parts are currently in manufacture,'' he said.