Knee defender protects legroom, the selfish way

Invented in 2003, the Knee Defender allows airline passengers to prevent the seat in front of them from reclining. While the controversial device has found favor with many tall travelers, it causes nothing but headaches for airlines. In the latest example, a heated skirmish over one passenger's use of the device resulted in a United flight's being diverted earlier this week.
The solution consists of two plastic clips, which the user simply places on the arms of the folding tray table in front of them, thus preventing the passenger ahead from reclining their seat back.
Plenty of long-legged travelers have come to see the gadget as an essential item in their carry-on bag. Naturally, though, the device has been met with less enthusiasm from passengers on the receiving end, who don't appreciate being forced to remain in the upright position.
The US Federal Aviation Administration has declared that the Knee Defender is not against federal aviation law, leaving it up to individual airlines whether to ban the device. Most American airlines, including United, have prohibited its use, although enforcing the ban is not always easy.
Source: Relaxnews