Record numbers of people have crossed New Zealand's border in the last few months.

Customs Minister Nicky Wagner says the 2014 to 2015 summer season has been the busiest so far.

More than three million international travellers arrived and departed from the country's airports between December and February.

That's an increase of just over 6% on the previous summer.

The government's happy with its recent investment in border control technology, with almost all travellers processed within 45 minutes.

Almost 10 million items of international mail were also cleared over summer, a significant increase on last year.