But critics of the Badgerys Creek site in the city’s far western outskirts are ramping up their attacks on the plans, which are expected to be rubber-stamped by the federal cabinet on Tuesday.
A second Sydney airport has been on the cards since the 1970s in a bid to take pressure off Mascot's Kingsford Smith Airport, which is subject to a curfew between 11pm and 6am.
Western Sydney Airport Alliance spokesman David Borger said the decision to build at Badgerys Creek, some 50km west of the CBD, was long overdue.
He said local residents would support the decision because it will create jobs and raise living standards.
Liverpool Mayor Ned Mannoun said locals were sick and tired of hearing about an impending decision and want construction to start soon.
"If this were to get delayed .... there is a chance that people will start saying `no, we don't want this anymore because more and more people are moving into the area'," he told ABC radio on Tuesday.
However, Western Sydney Labor MP Ed Husic said locals are being "blackmailed" into supporting the decision.
"They say `If you want better infrastructure you have to support the airport and by virtue of blocking the airport you won't get better infrastructure'," he told ABC radio.
And Stephen Bali from No Badgerys Creek Airport Inc said the local community will fight the decision once an announcement is made.
He has called for clarity on possible flight paths for residents set to be affected by noise pollution.
His group claims an airport at Badgerys Creek will increase pollution and could cause health concerns for local residents.
Aside from Badgerys Creek, other options for the second airport have previously included Wilton, in Sydney's southwest.
Experts have also considered expanding the RAAF base at Richmond, in Sydney's northwest, or building a high-speed rail link between Sydney and Canberra Airport.
A new airport - wherever it is built - would cost billions of dollars and would likely require significant upgrades to local transport infrastructure.
Reports have suggested that a bulk of the funding for the project could come from the private sector.
It remains unclear if the federal government will confirm its decision on Tuesday. The NSW government says it is planning no announcements on the subject.