IATA also says the currency is expected to remain weak.
"The weaker pound has immediately made outbound and uncertainty has immediately made outbound trips for UK inhabitants more expensive."
In 2014, 880 million passengers were carried by air in 2014 in the European Union with Britain reporting the highest number, 220 million.
That could mean fewer visitors here from Britain, New Zealand's fourth biggest tourist market.
In the past year, 213,000 came here, up nearly 8 per cent on the year before.
However, Tourism Industry Aotearoa says the market was resilient.
"We don't expect the outcome of the Brexit vote to have a significant impact on New Zealand tourism," said chief executive Chris Roberts.
Almost half of those visitors (101,600) came to visit friends and relatives, and that market was relatively resilient to any change in economic conditions or confidence.
The tourist industry here is expecting a windfall from next year's Lions Tour which is expected to attract 20,000 fans.
Roberts said many of the packages had been sold already.
While it's tougher for Brits to come here, the appreciation of the kiwi dollar against the pound - and the Euro - has made a trip there more affordable for Kiwi travellers.
The kiwi was this morning buying 52.44 British pence and 64.30 euro cents.
About 150,000 went to Britain last year and House of Travel's Brent Thomas has said he's expecting a spike in bookings this week.
