Passenger traffic on U.S. carriers is expected to nearly double in the next two decades,

according to Federal Aviation Administration projections released Thursday. FAA forecast revenue passenger miles, which represent one passenger paying to fly one mile and are a key indicator of traffic, to grow to 1.57 trillion in 2032 from 815 billion in 2011, "with an average increase of 3.2 percent per year," according to FAA. Meanwhile, the total number of passengers flying on U.S. commercial airlines is expected to increase this year by a modest 0.2 percent to 732 million and by an additional 2 percent year over year in 2013. "The aviation system is expected to reach one billion passengers per year in 2024," according to FAA, whose forecast "underscores the need to continue moving forward with implementation of FAA’s Next Generation Air Transportation System."