A federal appeals court is now ordering the FAA to look into it and determine if there's a safety issue.
Airline regulators cannot set minimum standards for comfort.
But a group of passenger rights advocates say the shrinking legroom and width of each seat has become a hazard.
"It does not appear that people can get out with the smaller seats. Most recently there was an evacuation for a burning engine in an aircraft, and it took about five minutes instead of 90 seconds," Paul Hudson said.
The group also claims the tight fit puts passengers at higher risk of blood clots in their legs.
Flyers Rights says seats have gotten an inch and a half narrower since the early 2000s and the space between seats has shrunk an average of four inches, from 35 inches to 31 inches.
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