Southwest Airlines is expanding its service at Portland International Jetport, adding seasonal nonstop flights to Chicago and Nashville beginning this spring.

The airline plans to offer flights to Chicago Midway International Airport on Saturdays and Sundays. It also will introduce a Saturday flight between Portland and Nashville. The limited service will run from June 7 through Aug. 10.

“Today’s announcement from our partners at Southwest is fantastic news,” Jetport Director Paul Bradbury said. “Many of our airlines are adding service for this upcoming summer and the expansion of Midway and new service to Nashville will provide Southwest passengers with more options to access the Maine market.”

Baltimore is the only city that Southwest serves with year-round nonstop flights from Portland.

The number of nonstop flights to Portland has increased markedly in the last few years as the city has grown as a tourist destination and food and beverage hot spot. In the last year, American Airlines offered summertime flights to Dallas-Fort Worth, United did the same for Denver,  and Sun Country has announced a seasonal service to Minneapolis.

Summer, the height of Maine’s tourism season, is the busiest period at the Jetport. Almost 936,000 passengers flew through Portland from June through September in 2018, nearly half of all the 2.1 million passengers that year.