Next time you board a commercial flight, don't expect to find an empty seat next to you.
The nation's carriers filled an average of 83.1 percent of the seats on flights in 2013, according to the U.S. Bureau of Transportation Statistics.
The high rate, known as the load factor, indicates that the number of seats made available by airlines is not keeping up with increased demand.
The nation's airlines carried 743 million passengers in 2013, the highest annual total since 2008, according to the federal agency. By comparison, U.S. carriers flew 737 million passengers in 2012.
Meanwhile, the number of flights dropped from more than 9.3 million in 2012 to slightly less than 9.2 million last year, the agency reported Thursday.
The biggest load increase came from international travel on U.S. carriers, which grew by 3.3 percent, while domestic travel rose by only 0.5 percent, according to bureau data.
The crowded conditions on planes are not likely to ease - air travel is expected to soar in the next 20 years.
The Federal Aviation Administration released a forecast Thursday that predicted commercial air travel will grow at an average pace of 2.8 percent the next 20 years.
The FAA predicted load factors will rise to at least 84 percent by 2034.