FBI spokesman J.J. Klaver said, "It's something that the average person is not going to see very often, if ever."
According to Wikipedia, "the hand-tefillin, or shel yad, is placed on the upper arm, and the strap wrapped around the arm, hand and fingers; while the head-tefillin, or shel rosh, is placed above the forehead, with the strap going around the head and over the shoulders."
Although the teenager explained the device to crew members when questioned, the captain of the flight decided to divert to Philadelphia anyway. Flight 3079 left LaGuardia Airport in New York around 7:30 AM, and landed in Philadelphia about 90 minutes later. There, it was met by police and officials from the FBI and Transportation Security Administration.
The White Plains, NY teen, who was traveling with his 16-year-old sister, was very cooperative, and neither were booked into custody. Both were allowed to continue on their way, and passengers on the flight were re-booked on other flights.