Airlines fuming over Auckland Airport's billion-dollar plan to combine terminals, warn consumers will pay

Airlines are fuming over Auckland Airport's plans for a $3.9 billion upgrade.

The airport says the almost 60-year-old terminals are no longer fit for purpose - but Air New Zealand is warning the costly revamp will make airfares unaffordable for a large number of Kiwis.

For 57 years it's been the gateway to New Zealand but those in charge say it's time to join the 21st century.

"And as the world continues to evolve so must we," Auckland Airport's CEO Carrie Hurihanganui said.

"Come with us on our journey as we advance the next 10 years of Auckland Airport's transformation building the gateway New Zealand needs to thrive and grow."

Replacing it with a $3.9 billion combined terminal.

"It is constrained the ability for passengers to cope with the volume and the demand that's coming through, people finding long processing times, it is old and just purely that view if we're thinking about growth that airlines are aspiring to, this is not going to deliver that," Hurihanganui said.

Despite being only at 85 percent of 2019 capacity, the domestic terminal still gets very busy.

Part of the problem is the notorious green line between domestic and international terminals. Rain or shine, first-class or cattle class, it's a journey people have to negotiate.

Travellers can either take their chances waiting for a shuttle or it's a ten to 15-minute hike with an overladen trolley.

There are plenty of complaints and it is what makes New Zealand look third world to first-time visitors, hence the plan to join up the terminals.

"It'll be easier more intuitive, there'll be more space for passenger processing, nobody likes queues," Hurihanganui said.

"A lot of move towards a more sustainable airport but also just a more seamless experience for our customers."

But there's no such thing as a free ride and airline landing fees will have to increase to pay for the upgrade - but by how much will be down to the Commerce Commission.

"And we're also 3 to 4 percent of the domestic airfare, the average price, so it's quite small in the scheme of things but yes there will be an increase to airlines," Hurihanganui said.

The airlines said they will be forced to pass on those costs - but fear they'll be substantial and as a result, some passengers will ultimately be priced out.

"In particular it'll affect the lower-priced airfares," board of airlines representatives executive director Cath O'Brien said.

"You know those are the fares that may no longer be available and certainly, our economic analysis suggests that a lot fewer people will travel."

The new-look airport could open in 2028 or 2029 and with a new look, there's often a new name - which the bosses haven't ruled out.