Charleston International Airport is nowhere near the top division of airports in the country based on passenger count.

But it's on approach.

The Federal Aviation Administration and the Transportation Security Administration place airports into different categories: "X" for those with more than 5 million departing passengers; "I" for those between 1.25 million and 5 million; "II" for those under 1.25 million.

Huge cities like Atlanta, Chicago and Los Angeles fall into the "X" category.

Charleston International, the state's busiest airport, is now a Category I airport, rising to the mid-tier group for the first time, said Bill New, airports deputy director.

Through the 12 months that ended in June, slightly more than 1.35 million passengers boarded a plane at CHS. An almost equal number arrived, but the federal agencies categorize airports based on the number of departing passengers.

Besides rising a notch, the classification gives the airport a little more industry clout.

"There is a very good likelihood that we will have access to additional funding that we normally wouldn't receive," New said. The new rating might also result in stiffer security requirements, such as more frequent testing and updating of emergency plans, he said.

With the addition of carriers such as Southwest Airlines and JetBlue Airways, the growth of Boeing and accolades heaped on Charleston as a national and international tourist destination, the number of passengers is expected to grow steadily over the next few years, possibly doubling by 2030.

The Aviation Authority projects the number of boarding passengers to increase 29 percent to 1.74 million by 2022, for an average annual growth rate of 2.9 percent. That projection is based on population growth of 2.3 percent each year through 2022.

To meet that growth, the airport terminal is expanding.

Charleston International is in the throes of a $189 million makeover, adding five new gates, a third baggage carousel, consolidated security checkpoints, new rental car pavilion, dome over the lobby and cosmetic changes to update the 29-year-old building. Construction is expected to be done in August 2015.

Reach Warren L. Wise at 937-5524.