Does it feel more crowded on airplanes these days? FRED has some data on that. Specifically, we look at “load factor,” an industry term for passenger-miles as a percentage of available seat-miles, which measures how full a flight is.

The graph offers data for domestic and international flights that have clearly not been seasonally adjusted. Just look at all the turbulence: Summer months are highly popular; international flights are much less full in February; and domestic flights seem to do a double dip, first in September and again in January.

But back to our question: Yes, flights seem to be slightly fuller than before. The load during popular months hasn’t risen much. But low-load months, especially domestically, have seen large increases. So your seatback may be in the upright position more often than not. Still, it may be more likely that you’re simply on a popular, crowded flight and not more likely that every flight will be more crowded.

The most extreme signal in this graph, of course, is the steep decline in airline travel after September 11, 2001.

How this graph was created: Search for “load factor,” select the two series you want, and click “Add to Graph.”

Suggested by Christian Zimmermann.