A report on the future needs of Sydney airport has found the current site will reach aircraft gridlock in peak hours by the end of the decade.
Peak-hour capacity at the current airport will be reached within eight years, if nothing is done.
The joint report by the federal government and New South Wales government says a second airport will be needed within 18 years.
It has found Badgerys Creek, in west Sydney, remains by far the best option.
That site has been repeatedly ruled out so the committee put forward Wilton, south of Campbelltown, as a next best option.
In the short term, the committee said peak-hour aircraft movements should increase from 80 to 85 per hour at Sydney airport, but the curfew should remain in place.
The report also said more passengers must use public transport to get there.
Another interim measure is to begin passenger plane services from Richmond Air Force base in north-west Sydney.