Proactive thinking and action has made US declare that mobile phones without charge are a threat to US security. CNN wrote:

Our job is to ... try to anticipate the next attack, not simply react to the last one. And so we continually evaluate the world situation, and we know that there remains a terrorist threat to the United States, and aviation security is a large part of that, Johnson told NBC's 

I will pass the rest of the details and assume that a certain terrorist has made a bomb in the form of a mobile device. Imagining this reminded me of an incident I witnessed in Nakuru about two or so years ago.

A boda boda rider was given a luggage to drop at one of the busiest back streets in Nakuru, a distance of less than one kilometre from where he was given the luggage. The owner of the luggage offered to pay him Shs 500, 10 times more the normal rates. The boda boda rider, being suspicious, insisted that he'll only deliver the luggage if he was accompanied by the owner. The owner obliged and jumped onto the motor bike, and off the rider went, not to the requested destination, but to Nakuru Central Police Station.

The police officers received the luggage and after obtaining necessary details, demanded the owner to open it up - in an open arena. What if it was an explosive? Realizing the risk I quickly ran out of the police station - luckily the luggage, I was later informed, didn't contain any explosives nor illegal items.

But the two officers from Pangani Police Station who decided to drive in a suspiciously driven vehicle in April this year were not as lucky. The vehicle, loaded with explosives, was driving on the wrong side of the road along Thika road, was stopped by the police officers, two of them got into the vehicle, and demanded the driver to drive to Pangani Police Station. Sadly, when the vehicle was entering the police station, the explosives went off killing all on board and injuring others.

So back to the requirement that all mobile phones headed to US must be turned on at the departure airport. What happens when your phone can't turn on?  The Telegraph writes,

British Airways said passengers who fail to turn on devices when asked will be immediately banned from their US flight and have to reschedule, even if they offer to abandon the item or send it on separately...even a new device bought in the airport lounge after passing through security will have to be charged up or the passenger will not be allowed to board at the gate. Any transfer passenger whose device has gone flat on the first leg will also be prevented from their onward travel unless they can recharge first.

The question is, what if there is this terrorist who has actually made a phone bomb that goes off when the phone is turned on (maybe a very powerful one). He is forced to turn it on, and he does...I am not sure whether TSA , or Homeland Security that directed it, is aware of suicide bombers.

What if it is an Explosive and it Does Work. Luckily they checked. Airport Quality Control.

Wrote a commenter on the CNN article.

If you asked me, asking travelers to turn on their electronic devices is not the wisest thing US Homeland Security has come up with. Actually turning on phones at the airport is the security threat. It seems the US Security officials have reduced themselves to a reasoning level of our own local police.