The US Transportation Security Administration has added additional security regulations for customers flying to the United States from points abroad. Travelers with any electronic or battery powered devices (mobile telephones, tablets, e-books, laptops, etc.) may be required to turn on their device in front of security teams and/or demonstrate the item's functionality.
If, when asked to do so, customers are not able to demonstrate that their device has power, they will not be allowed to fly with their electronic device.