It's not an optical illusion: Airplane cabins are becoming more crowded.
Over the past 40 years, airlines have cut seat pitch in order to fit more passengers on board.
That wasn't always the case.
In the early days of commercial flights, in the 1920s and even in the 1930s, airplane seats were just wicker chairs. After that the chairs were made of aluminum. They looked nothing like the airplane seats we're used to today, but more like a chair you could find in someone's home.
During an economic boom after World War II, more travelers took to the skies and manufacturers introduced larger planes with big, cushioned seats to match. There was only one class of flying. The two-class cabin came a little later, as more travelers opted to fly over taking a bus or a train.
Seat pitch, the distance between the back of one seat to the seat in front of it, was about 35 inches in the middle of the 20th century, according to Bob van der Linden, chairman of the aeronautics department at the Smithsonian Institution's National Air and Space Museum.
The race to cut seat pitch began in earnest after the U.S. deregulated the industry in 1978.
While the smoke-filled cabins of the 1960s and 1970s were certainly roomier, air travel was very expensive. When they were regulated, the U.S. government set airfares. A transcontinental flight cost more than $1,000 in inflation-adjusted dollars in the mid-1970s, while travelers could find tickets for around $300 for the same route today. Airlines back then, however, did not charge for checked luggage, seat selection, or myriad other add-ons they do today.
After deregulation in 1978 airlines competed on price, so more and more passengers were stuffed into planes.
The industry rode through boom and bust cycles, faced bankruptcies and consolidated, leaving four airlines in control of some three-quarters of the U.S. market.
In the 1980s, seat pitch was more than 33 inches, by the 2000s seats had 32-33 inches of pitch and today they're at about 31 inches, according to SeatGuru.
Some budget airlines offer less than that. Spirit's seat pitch, for example, is about 28 inches, among the lowest in the industry. Spirit has seats that don't recline, and the airline has argued the seat design makes the seat feel like more than 28 inches of room. Other airlines are opting for slimline seats too that forgo seat-back entertainment systems on some routes.