Auckland Airport chief Adrian Littlewood says a second runway is critical to the future of the company and to the city.

The airport yesterday announced a 17 per cent increase in first profit to $165.9 million and has just publicly notified revised plans for another runway to the north of the existing one.

Littlewood said the new runway had long been part of plans for more aircraft and had just embarked on another step in the process that has been running for the last 20 years.

''Fundamentally if Auckland wants to be an international grade city you've got to have that connectivity,'' he said.

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''It's really important that we as custodians of this asset for the future do the right thing for over 30 to 40 years.''

The number of passengers through the airport is forecast to grow from around 19 million to 40 million a year by 2044. Concerns have been raised about more noise but Littlewood said the modified plans had the same operating hours (7am to 10pm) that had been consented several years ago.

New-generation aircraft were quieter than the ones they replaced, he said.

Littlewood said the company had budgeted $200 million for design, engineering and planning work for the runway that could be up to 2983m.

The cost of building the new runway had not been released and is separate to the $1.8 billion spend on infrastructure in the five years to 2022 as part of its Airport of the Future project.

In the six months to December 31 revenue climbed 6.9 per cent to $332m, which the company said reflected a 2.7 per cent increase in aeronautical revenue to $59 million that was "driven by passenger growth and increasing runway movements".

Passenger services charges — paid by departing travellers through their airline tickets — were up 3.7 per cent to $89.1m.

Retail income was up 10.2 per cent to $88.9m, car park income up $8.7 per cent to $31.4m and investment property rental income up 16.3 per cent to $37.8m.

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Littlewood said the slower rate of growth of new airlines flying here in the past year was expected but there were other potential new carriers on the horizon and existing services were being expanded.

The halting of transtasman flights by Emirates' A380 superjumbos in March would be felt in the current half-year but he was hopeful that airline would expand its direct flying between Auckland and Dubai.

Auckland Airport will lose the Emirates transtasman flights in March. Photo / Dean Purcell
Auckland Airport will lose the Emirates transtasman flights in March. Photo / Dean Purcell

Developing markets including India and Korea were expanding quickly and the Chinese market was growing following a pause around the middle of the year when travellers deferred travel prior to visa rule changes that now makes travel here easier.

Auckland Airport's share of underlying profit from associates rose 47 per cent to $11.2 million, with strong growth from Queenstown Airport, its share of the Novotel hotel and contribution from North Queensland Airports, which it is in the process of exiting.

The company said full-year underlying profit would be in a range of $250m to $257m, narrower than the $248m to $257m estimate it gave at the time of its 2017 results.

The company will pay a fully imputed interim dividend of 10.75 cents a share, up 7.5 per cent from the same time last year.