Auckland International Airport Ltd. will invest NZ$27.7 million ($19 million) buying a 25 percent stake in Queenstown Airport, which has the nation's fourth-largest number of international visitors with its proximity to the South Island.

New Zealand's largest airport services firm will subscribe to new shares and has an option to raise its stake to as high as 35 percent as part of a strategic alliance, it said in a statement to the New Zealand stock exchange.

The NZ-listed firm's Chief Executive Officer Simon Moutter said: "We can accelerate growth in international passenger volumes by forming deeper partnerships with selected and like- minded airports that share our growth focus on particular airlines and travel markets."

Since the two companies established their informal mutual cooperation last year, a 36 percent increase in passenger traffic between the two airports has been recorded, Moutter said.

Auckland is the arrival point for more than 70 percent of New Zealand's visitors. The ASX listed company is investing in new terminals and alliances to help increase traffic. In January, it bought a 25 percent stake in two airports in Australia's Queensland state. On the other hand, Queenstown had 811,460 passenger movements in the year ended June 30, according to today's statement.