PHOENIX — Southwest Airlines is expanding its presence at Phoenix Sky Harbor International Airport.

The airline announced Wednesday that a new eight-gate concourse will be added to the airport's Terminal 4. Southwest already operates 24 gates at the Phoenix airport.

Sky Harbor officials say the concourse will be Terminal 4's eighth and final concourse. The new concourse is slated to open in 2021.

In addition to the new gates, Southwest also plans to double the size of its maintenance center at Sky Harbor, going from two bays to four. The maintenance expansion paired with renovations to the airline's provisioning center and ground-service equipment facility is expected to cost $40 million.