Profits are up but service at Australian airports has fallen across the board and Sydney Airport is the busiest and worst performing, the consumer watchdog says.
The Australian Competition and Consumer Commission looked at quality, prices, costs and profits related to aeronautical and car parking services at Adelaide, Brisbane, Melbourne, Perth and Sydney airports.
Its latest Airport Monitoring Report found a decrease in on-time flights over the last 10 years, and warned that congestion will increase without extra investment.
For the first time since 2008, no airport was rated "good" or better, despite passenger numbers and revenues rising at every airport except Adelaide.
"It is apparent that continued growth in passenger numbers at most airports is placing pressure on existing aeronautical infrastructure, contributing to lower service standards," ACCC chairman Rod Sims said.
"More investment is required to avoid excessive congestion, and ensure that the needs of Australia's travellers can be adequately accommodated."
Mr Sims said Sydney Airport, which received 36 million passengers through its doors and was both the busiest and lowest-rated airport in 2011-12, was "perhaps of greatest concern".
But in a statement Sydney Airport said the report found passenger satisfaction was at a 10-year-high and added it had invested more than $2 billion in airport-related infrastructure in the past decade.
"In fact, Sydney Airport was the only airport to have increased its passenger rating this year, a result of the investments we've made to add capacity, streamline check-in, screening and arrivals processes and add value for passengers, including free WiFi and improved terminal facilities," Sydney Airport CEO Kerrie Mather said in a statement.
The peak industry body, the Tourism and Transport Forum (TTF), said the nation's major airports were delivering crucial infrastructure at no cost to taxpayers. "As the ACCC report notes, Australia's five biggest airports spent $550 million on aeronautical assets (in 2011-12)," acting chief executive Trent Zimmerman said in a statement.
"That is not a one-off investment either, with plans for new runways at Brisbane and Melbourne Airports, and a terminal reconfiguration for Sydney Airport."