Air New Zealand is confident that its new Airbus A321s will be spared engine issues that have afflicted other airlines around the world.
Its first A321neo (new engine option) is due for delivery within weeks, after a year-long delay because of engine problems.
The aircraft is longer than the A320s used on domestic and short haul routes and is equipped with cutting edge Pratt & Whitney geared turbo-fan engines which are more efficient and quieter than existing engines, but have suffered teething problems at other airlines, particularly India's IndiGo.
Faulty seals have been blamed for the problem but Air New Zealand's head of aircraft programmes, Kerry Reeves, said the airline had delayed delivery to get more certainty.
''As with new products there are sometimes infancy issues as the engine matures and no engine is immune to those things. I think now they've reached a reasonably high level of maturity and reliability,'' he said.
Air New Zealand has for the past year been grappling with problems affecting Rolls-Royce engines on much of its Dreamliner fleet and was being cautious with the new power plants for the A321s which will be used on Tasman and Pacific routes.
''The latest version of the engine with the highest level of improvements is basically very reliable,'' said Reeves.
The single-aisle A321 plane being readied for delivery by Airbus in Hamburg will be the first of seven to join the fleet over the next year.
They are 7.5m longer than A320s and will have 46 more seats in what Reeves says is a completely revamped interior.
''The concept of the neo is that it's very simple and it's something that many airlines operate around the world, however we felt we had the ability to make a significant change so we introduced a lot of our widebody research and thinking to the interior of the aircraft.''
The slimline seats - upholstered with leather from Taranaki - are wider than those on existing A320s.
The middle seat will be 49cm - 3cm wider than the middle seats on the airline's existing A320 short haul fleet - and the aisle and window seat 47cm - 1 cm wider than now.
This doesn't mean the aisle is narrower on the all-economy class plane. The additional width is a combination of a slightly narrower armrest and extending the seat structure further outboard.
Seat pitch (the distance between them, fore and aft) ranges from 29 inches to 33 inches (74-83cm) compared to 30-34 inches in A320s used on international flights.
Reeves said this added up to around a 7 per cent increase in personal space, which was ''a really important part of the travel experience".
He said the wider middle seat more fairly allocated personal space.
"With the aisle or the window seat, you by default get a little bit of extra space than is devoted to the middle person.''
Air New Zealand had also developed a new way of reclining the seats, with a sliding lever around knee level to activate the 5cm recline.
''Reclining the seat is one of those interesting, polarising thing that our passengers talk to us about - they want to have the ability to recline if they want, but they don't want people to come too far into their space,'' said Reeves.
The lever was much easier to use than the traditional button, which was sometimes hard to find and difficult for some people to use.
''This is innovative and the first time anyone has developed this,'' he said.
Overhead bins were bigger, with 25 per cent more space, partly because emergency equipment would be stored elsewhere.
Seat-back inflight entertainment screens were larger and there was a quick USB charging port. Tray tables had also been modified to better cater for the mix of business and leisure travellers.
Air New Zealand is investing in 13 Airbus neo aircraft (seven A321neos and six A320neos) to replace the A320 fleet that provides short haul and domestic services, and a further seven Airbus A321neos for anticipated domestic network growth.
At current list prices, the combined value of the two aircraft orders is $2.8 billion, although airlines typically get significant discounts on this.