Southwest Airlines is already one of the two top airlines at Phoenix Sky Harbor Airport — and now the carrier is planning additional investments at the airport.

Southwest has made two big commitments to Sky Harbor. The first is that it will occupy a future eight-gate concourse at Terminal 4 set to open in 2021.

The second is that the airline will invest $40 million to expand its maintenance facilities at the airport. And both are big deals, said Deborah Ostreicher, assistant aviation director for the City of Phoenix.

“When an airline decides to double the size of their maintenance facility and commit to eight new gates on a brand-new concourse, that sends a message loud and clear that they are committed and invested in Phoenix,” she said.

These investments will not only help the airport, Ostreicher said, but also the economy in the city and state. The airport’s economic impact is estimated at $30 billion.