CHANGSHA, China — The cavernous rail station here for China’s new high-speed trains was nearly deserted when it opened less than four years ago.

Not anymore. Practically every train is sold out, although they leave for cities all over the country every several minutes. Long lines snake back from ticket windows under the 50-foot ceiling of white, gently undulating steel that floats cloudlike over the departure hall. An ambitious construction program will soon nearly double the size of the 16-platform station.

Just five years after China’s high-speed rail system opened, it is carrying nearly twice as many passengers each month as the country’s domestic airline industry. With traffic growing 28 percent a year for the last several years, China’s high-speed rail network will handle more passengers by early next year than the 54 million people a month who board domestic flights in the United States.

Li Xiaohung, a shoe factory worker, rides the 430-mile route from Guangzhou home to Changsha once a month to visit her daughter. Ms. Li used to see her daughter just once a year because the trip took a full day. Now she comes back in 2 hours 19 minutes.