The Knee Defender Device is a pair of plastic clips that you bring onto an airplane and slide onto the arms of your tray table, for the express purpose of preventing the person in front of you from reclining their seat. The cost for the clips are $21.95 and are allowed by the Federal Aviation Administration, as long as the airline involved will permit their use. Surprise: Most airlines will not allow passengers to use the clip!

The fight started on a United Airlines flight because one passenger was using the Knee Defender, a $21.95 gadget that attaches to a passenger's tray table and prevents the person in front of them from reclining. The dispute on United Flight 1462 from Newark, New Jersey to Denver escalated to the point where the airline decided to divert to Chicago's O'Hare International Airport, according to Transportation Security Administration spokesman Ross Feinstein.

Chicago Police and TSA officers met the flight, spoke to the passengers — a man and a woman, both 48 — and "deemed it a customer service issue," Feinstein said. The TSA would not name the passengers. The plane then continued to Denver without them, arriving 1 hour and 38 minutes late, according to the airline's website.