American travelers are flying on the some of most packed domestic flights in the world.

U.S. domestic flights were 83.8 percent full in 2013, more than the international average of 79.9 percent, according to data released today by the International Air Transport Association.

Passenger load is calculated as an average which means it includes that almost empty flight between two nearby cities and those packed flights flown home for the holidays.

It might not feel like it, but it also means that almost 20 percent of seats go unused on U.S. domestic flights.

U.S. load factors decreased in the middle of the year before picking up in the fourth quarter, but overall levels remained more stable throughout 2013 than 2012.

A rise in passenger traffic boosted the rebound in load factor.

Most Packed on the Planet

U.S. domestic flights have the highest passenger load of any of the individual countries looked at in the year-end report.

Screen Shot 2014-02-06 at 12.30.12 PMChinese domestic flights were 80.3 percent full and Australian domestic flights were 76.5 percent full.

Brazilian airlines cut capacity to mitigate the impact of declining domestic consumption, which in turn had boosted load factors to 76.3 percent, a 4.5 percent drop from 2012.

Photo Credit: Empty seats on a Southwest flight departing from Oakland Airport. Derrick Coetzee / Flickr