Improved economic growth will help U.S. airline-passenger numbers reach 1 billion per year by fiscal year 2021, according to Bloomberg.

The Federal Aviation Administration (FAA) released its annual forecast today, which said total passengers reached about 713 million in the year ended in September, and will increase at an average annual rate of 2.8 percent for the next two decades.

“Only a modernized air transportation system will be able to keep up with our forecasted demand,” FAA administrator Randy Babbitt said in a statement.

Leading to the increase in passengers, the agency said, will be an increase in the average gross domestic product during the next 21 years, projected at 2.7 percent per year.

The FAA predicted that the number of passengers who board flights in the United States this year will rise 3 percent, and then will rise 2.5 percent annually for the next 20 years.

The FAA in 2000 and 2001 predicted that the United States would top 1 billion passengers by 2010; that milestone wasn’t expected to be reached until 2023 in last year’s forecast.