The Federal Aviation Administration (FAA) has predicted that U.S. Airlines will see a 3.5 percent increase in the number of travelers this year and expects 1 billion passengers by 2021.

The total revenue passenger miles -- equal to the revenue from flying one passenger one mile -- is predicted to more than double to $1.7 trillion by 2031.

The reports said, “Commercial air carrier domestic revenue passenger miles (RPMs) are forecast to grow 3.5 percent in 2011, and then grow at an average of 3.1 percent per year through 2031; domestic enplanements in 2011 will grow 3.0 percent, and then grow at an average annual rate of 2.5 percent for the remainder of the forecast.”

The annual travel forecast released on Tuesday covers the next 20 years future of airline growth. The next five years' growth will average 3.7 percent per year with average annual growth of 2.5 percent per year, according to the report.

One factor that has influenced the recovery beyond prior forecast levels is stronger than expected traffic results during the latter part of 2010. Also the FAA said that U.S. carriers flew 635 million passengers on domestic flights in 2010, which was better than last year.

Airline profits topped $4 billion in 2010 on stronger demand vying for fewer flights at higher fares. But rising fuel prices this year have prompted some concern within the industry about future earnings.

Previously, the FAA predicted 1 billion passengers by 2010, but after the terror attacks of September 11, skyrocketing prices for fuel and a global recession, the expected date was moved back to 2013, then to 2015, again to 2016 and further to 2021.

But the present prediction is expected to hold up with the growing economy and rising employment rate.