A Knee Defender, a flying gadget that prevents the person seated in front of you on a flight from reclining, caused a fight between two passengers on a United Airlines flight.

Knee Defender Starts Fight On Airplane

En route from Newark to Denver, a male passenger whipped out the Knee Defender and affixed it to the chair in front of him, where a woman was seated, reported ABC News. The man, who was using the space to use his laptop, refused to remove the device to allow the woman to further recline. In response, the woman picked up her cup of water and poured it on him.

Due to the in-flight altercation, the United Airlines Flight 1562 was forced to land at Chicago’s O’Hare International Airport, according to Transportation Security Administration spokesman Ross Feinstein. In the end, the dispute was deemed “a customer service issue.” No arrests were made, though the Federal Aviation Administration could impose a civil fine of up to $25,000 for each of the passengers for behaving in a manner that forced the plane to ground.

The Knee Defender, invented in 2003 by Ira Goldman, a 6’3’’ American who was tired of his knees getting bumped as people reclined their seats, retails online for $21.95. The FAA allows airlines to make their own rules regarding the device, which is banned by all major U.S. airlines. On the Canadian airline WestJet’s website, the Knee Defender is specifically mentioned and prohibited, reported CNN.

"You are not permitted to attach any unapproved device to any part of your seat or any other part of the aircraft," says WestJet. "Some examples of unapproved devices include knee defenders, seat belt extensions and booster seats."