Moutter is leaving to lead Telecom in four months and has been praised by analysts for his role in increasing revenue from retail and property development.
The company also successfully actively sought out airlines to fly new services into the airport at a time when global aviation was facing reduced demand and high fuel prices.
"There was a lot of skepticism about the ability of airport companies to go out and proactively drive route development," Withers said.
He also led the company into investment in airports in Queensland and Queenstown.
Moutter was paid a base salary of $936,000 last year.
There would possibly be internal candidates, while the international search would focus predominantly on Australasia, Withers said.
Chief financial officer Simon Robertson will become acting chief executive when Moutter leaves.
The other big aviation vacancy is at Air New Zealand where chief executive Rob Fyfe will leave in December after five years at the helm. The hunt has been under way for the past three months to find a replacement.
An announcement is expected around the middle of the year and analysts say there is no clear favourite emerging publicly.
Air New Zealand last week referred back to a statement made at the time Fyfe's departure was announced in January.
"We would expect significant international interest in the role and believe there are some very strong candidates from within Air New Zealand's existing executive management team," the airline said then.
Fyfe's base salary was $1,350,000 for the 2011 financial year.
Business commentator and executive director of Milford Asset Management Brian Gaynor said Air New Zealand's deep executive pool meant there was a stronger chance of an internal appointment at the airline.
"I think they'll be looking for similar-type people, a bit aggressive and innovative. What we wanted to get in New Zealand 10 or 12 years ago was very conservative, steady-at-the-wheel-type people."
Potential internal candidates include the head of short-haul airlines Bruce Parton, long-haul chief Christopher Luxon and head of human resources and engineering Vanessa Stoddart.
One analyst, who did not want to be named, said it was more likely the board would choose an overseas airline executive for the top job.