I saw this article and had to post it. 'While the Federal Aviation Administration does not prohibit the use of the Knee Defender, like most other major U.S. airlines, "we do not allow customers to use devices that prevent seats from reclining," said United Airlines spokesman Charles Hobart via e-mail.'
www.usatoday.com/story/todayinthesky/2014/08/26/knee-defender-fight-united-flight-diverted/14609109/