Air New Zealand says its urgent fix for troubled engines on its Dreamliner 787-9 fleet will take another month to complete.
Since two aircraft had to turn back to Auckland with engine issues in December, the airline has sent 13 engines to Rolls Royce facilities overseas for "unscheduled maintenance" - and has had to lease two A340 aircraft with different in-flight comforts to fly passengers to Sydney and Perth.
Some of the affected, engineless, Dreamliners have been parked at Auckland Airport as the massive engines are sent overseas.
An airline spokesperson has told Newsroom the extra, or unscheduled engine work is dealing with 13 engines but other engines would need to "cycle through Rolls Royce facilities" as part of its normal maintenance programme.
"We expect to have the full Boeing 787-9 fleet operating around mid-April."
Having leased the two A340s from Hi Fly, a European aviation company, Air NZ has offered passengers service levels different to its standard offering on the services to Perth and Sydney in the four months since the engine crisis.
Passengers report the in-flight entertainment system is a European menu of video and music and cabin service and comforts vary from Air NZ's advertised products.
The spokesperson said the airline had been contacting customers whose flights were scheduled to be operated by Hi Fly in advance, if Air NZ had contact details from their bookings. They were advised "on board products and service style will differ from what they are used to."
Those who no longer wanted to use a Hi Fly flight were offered alternatives including deferring travel until a later Air NZ aircraft could take them, for up to 12 months. If no alternative could be arranged a full refund was possible.
"This has been a challenging situation and one that has been beyond our control and we appreciate that our customers have been patient as we've managed through this maintenance work."
The two incidents within days of eachother in December included an engine on a Dreamliner bound for Tokyo having to be shut down when it caused the aircraft to shake violently. Passengers heard clunking sounds and the electrical power went out temporarily after takeoff from Auckland.
The second issue was on a flight to Buenos Aires, which had to turn back when problems arose with an engine, which did not need to be shut down.
The Transport Accident Investigation Commission is working on the twin incidents.
Air NZ told Newsroom at the time, after being shown the photograph above and others taken on the tarmac after the Tokyo flight returned to Auckland, that "damage sustained suggests an engine part has travelled through the engine".
Rolls Royce has about 400 of the Trent 1000 Pack C engines in service and told investors last year to expect "increased activity in the second half related to Trent 1000 maintenance programme to address a number of technical issues."
Air NZ emphasised to Newsroom its issue related to the engines not the 787 aircraft. "This is a worldwide issue affecting numerous operators of the Rolls Royce Trent 1000 Pack-C engine globally. Our strong relationship with Rolls Royce has been really helpful in getting these engines back into service."
The airline's chief executive Christopher Luxon wrote to customers last month saying of the engine problem: "Unfortunately over the summer weather has not been the only challenge the airline has faced. As many customers will be aware we have had to bring some of our Boeing 787-9 Dreamliner fleet into our engineering facilities for unscheduled maintenance work."
The airline will not disclose the costs of the disruption, saying they have been factored into its full-year guidance to investors "and they are not material."