Airplane seats have been shrinking, and now the Federal Aviation Administration (FAA) has been ordered to re-review whether seat size should be regulated.
The U.S. Court of Appeals in Washington, D.C., ordered the FAA to investigate what Judge Patricia Millett called "the case of the incredible shrinking airline seat," the order says.
“As many have no doubt noticed, aircraft seats and the spacing between them have been getting smaller and smaller, while American passengers have been growing in size," Millett wrote in the opinion.
The court's decision comes after the advocacy group Flyers Rights petitioned the FAA in 2015 to make rules about the minimum requirements for seat size and legroom, saying the shrinking space passengers have is endangering their safety, health and comfort (more on this below).
The FAA denied the petition.
But the federal appeals court ruled last week the FAA didn't have a reasonable basis for refusing the petition, saying the agency relied on outdated or irrelevant tests and studies to decide seat spacing was about comfort, not safety.
And because of that, the judges sent the issue back to the FAA, saying it must come up with a better response to the group's concerns.
Flyers Rights, a nonprofit, called the ruling "a victory."
The FAA, in a statement to Fortune, said "We are studying the ruling carefully and any potential actions we may take to address the court’s findings."
You can read the court's 23-page opinion here.
Here's how much seats have shrunk
Airlines have been making seats smaller in recent years to pack more seats on the plane, and as a result make more money, CNN Money says.
Flyers Rights' 2015 petition said seat pitch (how much legroom you get) has gone from an average of 35 inches to 31 inches, with legroom space being as narrow as 28 inches.
Meanwhile, the average seat width has gone from 18.5 inches to 17 inches.
You can see how each airline compares when it comes to seat pitch and width on the website SeatGuru.
Flyers Rights argues the average economy class airplane seat is designed for someone who is between 5-foot-9 and 5-foot-10, and is of average build. That's smaller than many Americans, with the group noting since the 1960s, Americans have gotten taller and wider.
Larger people and smaller seats puts travelers' safety at risk, the group argues. This can slow how fast people can exit in an emergency, as well as puts passengers at an increased risk of blood clots (which can be deadly), soreness and stiffness, the petition said.
The FAA said in its statement to Fortune it does consider seat pitch when making sure people can exit a plane quickly and safely.
CNN Money says no airline regulator in the world has made rules about seat size requirements. And if the FAA ends up setting standards for seating on commercial airplanes, it could be "the most significant government airline action since the industry was deregulated in 1979," The Consumerist says.
This issue could also end up in Congress. The Hill says the U.S. House is considering a proposal that would make the FAA set requirements for seat sizes and legroom on airplanes.