Sydney Airport has again boosted its fat profit margins from car parking over the past year, making it a standout among Australia's four largest airports for the fees it charges.

The competition regulator's latest annual report on the country's four major airports also found Sydney boosted revenue from the charges it imposes on airlines by almost 4 per cent to $17.27 per passenger last financial year.

It was the airport's largest increase in real terms in so-called aeronautical revenue per passenger since 2007-08, allowing it to further cement its title of the most expensive airport in the country to fly in and out of.

With Sydney Airport still deciding whether to take up its rights to build and run a new airport at Badgerys Creek, the Australian and Competition and Consumer Commission has warned a single owner will have an incentive to delay and restrict investment in Western Sydney Airport so it can boost returns from its existing operations.