When the person in front of you reclines their seat after takeoff, don't get angry, get The Knee Defender .

For a mere $22 dollars , this plastic gadget allows tall fliers to reclaim their kneecaps, with the slight possibility of starting a little trouble. The Knee Defender's tagline "standing up for the right of the tall guy to sit down" says it all, but doesn't really mention how the person in front of you will feel when you attach the plastic clips to your tray table.

Jarod & Jennifer Davis/flickr

A "controversial" gadget that's been on the market for a few years now, The Knee Defender hasn't completely caught on . As one website put it , the "two plastic clips could turn flights into fights." Luckily, the Defender comes with a 'Courtesy Card' that you can fill out and give to the person seated in front of you.

The FAA weighed in on use of the Defender in 2008, saying: "the clips were not against federal aviation rules as long as they weren't used during taxiing, takeoffs or landings.