Under a $950 million project preliminarily approved this week, Phoenix Sky Harbor International Airport will extend its automated train service to the rental-car center and add gates at Terminal 4.
The projects will be funded with existing passenger fees, other airport revenue and bonds and be completed by 2021.
Forecasts call for 48 million passengers at Sky Harbor in 2021, up about 9 percent from 44 million last year.
Terminal 4 currently has 83 gates. A new, eight-gate concourse in Terminal 4 has also been on the table since the terminal opened in 1990.
Airport officials say it's needed now to accommodate airlines' larger planes and reduce passenger congestion in the terminals.
The aviation advisory board unanimously approved the Sky Harbor plan. It now goes to the Phoenix City Council.