"Our infrastructure projects will add significant aeronautical capacity to cater for future growth – and we need to get them right."
The company hasn't changed its financial year guidance of $265 million to $275m.
Littlewood said the ongoing focus on design and planning has meant that spending on physical works has been later than expected and capital expenditure during the 2019 financial year was at the lower end of our forecast, coming in at $284.1 million against guidance of $280m - $330m.
There was not an update on when the second runway would be needed, "but we want to be firmly in a position to deliver it when it's required and on time".
Forsyth Barr analyst Andy Bowley said his firm continued to believe that the timing of the Northern Runway development would be pushed out.
The company's ability to charge for the runway in the 2021 financial year would be compromised.
"While the timing of commissioned capex may be later in the current pricing period than assumed at the time of pricing, the benefit to AIA's effective internal rate of return may be offset by lower passenger growth."
The reduced level of capex to date and through the current pricing period would have a bigger impact on the five year pricing period beginning July 2022, said Bowley.
But Littlewood said the company still expected to finish the five-year pricing period through to 2022 strongly, with total commissioned assets over the period broadly in line with the forecast released to the market in mid-2017.
"As an indication of the current momentum in our build programme, we now have both infrastructure and commercial projects with a combined value of over $1.1 billion underway."
He said the long-term trend was for travellers using Auckland Airport to double by 2044 – but changing market dynamics meant there would be fluctuations in growth rates between years.
While 2019 was another record year for travellers numbers grew at a slower pace compared to recent years, and there were several reasons for this.
"In a year of constant headlines about trade wars, Brexit, and civic activism, we saw different growth patterns emerge. Globally, passenger demand for travel has slowed, including in some of our key visitor source markets - Australia, China and Japan."
New routes to Asia and North America have been added – but the recent trend of rapid capacity growth is slowing due to airlines adjusting their business strategies to focus on yield over-capacity.
"This month was another example with Jetstar announcing it was pulling out of five New Zealand regional routes, reducing some important connections into the regions," said Littlewood.
Future growth projections remained strong.
Urbanisation and the growth of the middle class in India, China and Southeast Asia continued to represent a significant opportunity for our tourism sector over the long term.