The ASX-listed Sydney Airport on Tuesday released figures showing it posted the lowest growth in revenue from parking fees in at least five years .

Revenue from parking and ground transport grew 2.2 per cent in the first half of 2017 to $77.1 million, down from 4.4 per cent growth in the same period last year and a fraction of the growth enjoyed only a few years ago.

Sydney Airport chief executive Kerrie Mather said the drop off was primarily due to more people catching the train to the airport. Train passengers grew 14 per cent in June even as domestic airline passengers grew only 2 per cent, she said.

Despite parking and ground transport fees making up 11 per cent of the airport's revenue, Ms Mather said the airport would continue promoting rail as an alternative to driving or taxis because it would reduce congestion and improve passengers' experience.

"The Opal Card means that people are just using public transport more, and I think probably the roadworks in George Street having a significant impact on travel around the city at the moment is a factor as well," she said.

About 20 per cent of all passengers going to the airport used the train and Ms Mather said she would continue to push for more public transport options, pointing to London's Heathrow Airport where 40 per cent of all passengers arrive or leave on public transport.

A record 8.2 million passengers took the train to and from the Sydney Airport in 2016, prompting the NSW government to pledged an extra 200 services a week to cope with demand.

Australia's largest airport's half-year results released on Tuesday showed the strongest year-on-year inbound international passenger growth in 12 years, helping boost profits even as domestic passenger growth slowed.

Global growth targetted

International passengers grew to 7.7 million in the six months to June 30, up 7 per cent on the same period in 2016, while domestic passengers rose 1.3 per cent to 13.2 million.

That was a slowdown from the same period last year when international travellers were growing at 9.3 per cent and domestic travellers were growing at 5.3 per cent.

Thirty-six per cent of all passengers were international travellers but they were the source of 70 per cent of Sydney Airport's revenue, Ms Mather said.

Inbound passenger growth had been driven by new capacity opening up to China, Indonesia, Japan and Vietnam, which Ms Mather said were countries with large diaspora communities in Sydney, creating a stable and non-seasonal market of travellers visiting friends and relatives.

"Just in China for example, five years ago we were serving three Chinese mainland cities and today it's actually 15," Ms Mather said.

Retail earnings grew 14.3 per cent after it opened a new designer brand precinct in the airport's international terminal.

Moody's senior analyst Spencer Ng said he expected international business to remain the airport's growth engine, with traffic increasing in the mid-to high-single digit percentage rage and "underpinned by a combination of strong travel demand, as well as seat capacity additions that have already been announced by international airlines."

Profit after tax for the half was $167 million, up 4.4 per cent from the same half last year. The company upgraded its 2017 dividend guidance by 1?? to 34.5?? a share, up 11 per cent on the prior corresponding period.

Citi analysts said the financial results were largely in line with estimates, and that the continued international growth was a positive.

Shares closed up 3.36 per cent at $7.08.