Air New Zealand is facing up to two years of flight disruptions due to engine issues and the downstream effect will likely mean propellor planes flying passengers between major New Zealand cities. 

Two major routes have been put on pause, the airline has announced, and changes have been made to others as it works through the respective issues with some of its fleet.

The national carrier said it's having to adjust its schedule due to the grounding of 16 aircraft undergoing mandatory engine maintenance by aerospace company Pratt & Whitney.

It will pause flights to Seoul and Hobart from April and is reducing flights on other routes as well as moving aircraft between routes.

Talking to The Mike Hosking Breakfast on Tuesday, Air NZ chief executive Greg Foran said Pratt & Whitney had to accelerate the process of taking the engines off-wing and checking them.

It started with a telephone call five weeks ago, Foran said, when the Pratt & Whitney chief executive informed Foran that American airlines were having to take their engines off-wing and take them into workshops to get checked at a rate of about 4 times quicker than they expected

"They're not sure exactly how long this is going to last, some of these checks, but the indications at this stage is it's going to be about two years," said Foran. 

"Whilst there are no safety issues with the engines, taking them off-wing and having them come off much quicker means that the workshops just don't have enough capacity to get them all checked quickly enough."

Foran called the situation "really unfortunate" as 25 per cent of its fleet using those engines face being grounded on the tarmac at any one time for the next two years. 

"I hope it's quicker, the CEO of Pratt & Whitney hopes its quicker, but it's better to be transparent and organise ourselves around it - it's much easier bringing capacity on than what it is taking it off."

Hosking asked how material the effects of the changes would be for the average New Zealander, using an example of what he would notice if he booked a flight from Auckland to Wellington today. 

He noted it's the A320 and A321 models that were reportedly affected.

"It's unlikely you will notice anything," said Foran. 

"What you will notice is if you were booking to go from Wellington to Christchurch, you're probably not going to be going on an A321 - you'll be going on an ATR."

An ATR is an older model of plane that uses propellers, rather than jet engines and is traditionally used in New Zealand for shorter-haul flights between smaller townships. 

Foran said the Wellington to Christchurch route was most impacted, as some of the A321 planes used for the journey were being repurposed for flights across the Tasman to make up for the fleet's shortfall. 

Hosking asked if "this is pre-war" and remarked the propeller planes were something from the 1930s. 

"It's a wonderful plane," said Foran. 

"Unfortunately this situation is just one we're having to deal with, the most important thing to do is get people from A to B and do it on time."

Talking more generally about the airline trying to find it's rhythm in a post-Covid economic environment, Foran responded to a comment from Hosking about the engine situation and flight delays coming across as somewhat chaotic. 

He agreed the word "chaotic" was a reasonable term for the airline's operational woes and said he preferred to use the word "clucky". 

"What I'm seeing in this industry, and I've had to learn this pretty quickly, is when it's been shut down for a couple of years because of Covid, it takes quite a while to get it up and running," said Foran. 

"And,  it's not just one piece of it - it's airports and aircraft plane makers, engine makers, it's security and catering, every component of it is rattling."