One of Charleston International's growing air carriers is bringing back a seasonal flight next spring.

Dallas-based Southwest Airlines will resume Saturday service April 13 between the Holy City and the Mile High City, the commercial carrier announced Thursday.

Flights to Denver will continue through June 8.

Earlier this year, the airline offered seasonal routes in April and then boosted service to daily flights from June through August. It's too early to tell if it will tack on the daily summer legs again, since the booking schedule only goes through June 8.

Denver-based Frontier Airlines, which launched service in Charleston earlier this year, offers three flights each week to its home base.

Southwest currently offers three daily flights from Charleston to Baltimore, two to Chicago Midway and one each day to Nashville and Houston.

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Charleston International is the state's busiest airport, with 3.99 million passengers coming and going last year. It's expected to surpass that count and set a new record this year of more than 4.3 million, based on estimates from airport CEO Paul Campbell.

Through the first eight months of this year, 2.99 million people have flown in and out of Charleston.

Reach Warren L. Wise at 843-937-5524. Follow him on Twitter @warrenlancewise.