It may feel like every flight these days is packed to the gills — and that's certainly the way airlines want it  — but nearly 20% of seats on American domestic flights go unfilled.

According to newly published numbers from the International Air Transport Association (IATA), the passenger load factor for flights in the U.S. is 83.8%.

While lower than you may expect, that makes U.S. flights the most crowded in the world.

China isn't far behind with a load factor of 80.3%, Brazil climbed from 71.8% in 2012 to 76.% in 2013, and Japan reported by far the lowest figure, just 64.3%. The global rate for the domestic market is 79.9%.

That doesn't mean that 20% of seats on every flight are empty, naturally — so next time you fly home for Thanksgiving, don't expect to have any extra elbow room.

Other news from IATA that is good for the airline industry: Passenger demand climbed 5.2% between 2012 and 2013, with especially fast growth in the Middle East and Asia. Unsurprisingly, growth in the developed U.S. and European markets was slower.

There's more good news for airlines: IATA has predicted it will see its biggest profits ever in 2014, largely thanks to growing revenue from those terrible bag fees.

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SEE ALSO: Flying Today Is So Much Better Than It Was In The 'Golden Age' Of Aviation