A 10-year plan for Charleston International will be laid out for board members this week, and part of that vision will include the next major construction project in just a couple of years as the state's busiest airport continues to expand.

About a year after a new 3,005-space parking garage opens at the airport, work could start in late 2021 or early 2022 on a new wing of the terminal, airport CEO Paul Campbell said.

The number of gates and the cost of the project haven't been determined, but he said the addition could be built in phases as airlines need more space to handle the growing  number of passengers.

Preliminary plans call for the new concourse to be built where rental cars are now picked up and dropped off. 

"It's not if we will need it, but when we will need it," Campbell said. "With the passenger growth at the airport, we have exceeded expectations."

Over the past eight years, the airport averaged 10.6 percent more passengers coming and going each year, more than doubling to 4.47 million last year from about 2 million in 2010.

During the first three months of 2019, nearly 1 million ticket holders have traveled through the terminal. The forecast calls for about 4.8 million by the time the year comes to close.

A strategic plan laid out several years ago called for another wing with more gates by 2028. Campbell said the plan now is to have it completed by 2023.

Money for preliminary engineering and design work is being included in the airport's upcoming spending plan for the new budget year that starts in July.

The Charleston County Aviation Authority, which owns and operates the airport, added five gates to Concourse B when a $200 million makeover of the entire terminal was completed in 2016.

Concourse A was not expanded because aircraft navigating around it could potentially interfere with the taxiway used by Boeing Co. for its 787 Dreamliners that are assembled nearby.

"We can expand Concourse A, but that is a last resort," said airport engineering director Britton Corbin.

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Board member Paul Thurmond questioned the time frame of finishing the project by 2023, recognizing it is just a few years away.

Campbell said construction could move along faster than when the terminal was overhauled because it's in an area not used by the general public.

"The terminal work had to be done with passengers still using it," he said. "This is a greenfield project."

Charleston's airport is now served by nine airlines flying nonstop to 31 airports and 27 cities, including British Airways, which launched the first transatlantic flight between Charleston and London in early April.

New cities continue to be added to the nonstop lineup from the Lowcountry. Frontier Airlines launched twice-weekly service to Cleveland last Thursday, and Allegiant will offer twice-a-week flights to Ohio's capital of Columbus in June. Meanwhile, Delta Air Lines will add daily service to Minneapolis the same month.

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