Air New Zealand's issues have continued to make headlines in 2018, with customers unhappy with the calibre of planes covering the Dreamliner fleet while the aircraft receive maintenance.
Last year, an Air New Zealand flight to Japan experienced an engine abnormality, resulting in it returning to Auckland - then a week later an aircraft bound for Buenos Aires had a similar problem, and also returned to Auckland.
This brought about an urgent maintenance programme, meaning Air New Zealand had to schedule its Dreamliner fleet for lengthy maintenance in the lead-up to Christmas.
Engine manufacturer Rolls Royce said the cost of maintenance work reached around NZ$320 million in 2017, but it expected that amount to double in 2018 before tapering off in 2019.
The replacement aircraft are from European charter company Hi-Fly, and are operating on some flights between Auckland and Sydney and Auckland and Perth.
On the weekend, passengers spoke to Newshub about how untidy the aircraft were.
Air New Zealand says the current fleet situation, which it describes as "challenging", is no fault of theirs.
The airline says it's been proactively contacting customers who are due to fly on the Hi-Fly aircraft to inform them of the difference in the on-board experience, and have waived penalty fees for anyone who wants to change their flights to one operated with Air New Zealand aircraft. It has even offered credit and refunds.
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AirlineRatings.com have awarded Air New Zealand the title of best airline in the world numerous times, and its aviation commentator Geoffrey Thomas said the airline was left with very few options when the Dreamliner issue sprung up so close to Christmas - a time when airlines tend to maximise their fleet resources.
"Unfortunately Hi-Fly is just a charter airline, and is nowhere near the standard of Air New Zealand, [which] is the best airline in the world - and any other airline is going to compare badly."
Mr Thomas said although it's a drop in standards, he doesn't see it damaging the airline's reputation for award-winning customer service long-term.
Air New Zealand expect the Dreamliners to be fully back in action by mid-April, meaning the replacement Hi-Fly aircraft will no longer be needed.