ARE YOU TO KEEP YOUR ELECTRONIC DEVICES ON WHEN YOU ARE ON THE PLANE ?

Why Can't You Use Phones on Planes...?

As long as you're willing to pay for it, you can now do pretty much whatever you want on an airplane: Hop on Wi-Fi, watch movies, play video-games, and in some first-class cabins you can even, ahem, recline with a friend. So why can't you use a cell phone? Despite what fear-mongering flight attendants say, making a call probably won't send your plane on a collision course with a tropical island populated by smoke monsters and Evangeline Lilly.
Sure, your mobile can interfere with avionics — in theory. But in practice, it's far from likely. Cockpits and communications systems have been protected against electromagnetic meddling through safeguards like shielded wiring and support structures since the 1960s.
So why the resistance? Part of it, naturally, comes from the call carriers. When phones ping for signals at 35,000 feet, they can hit hundreds of towers at once, necessitating complicated parsing of roaming agreements. Providers don't want the hassle if they're not being properly compensated, so the government has left the plane ban in place.

Reference: http://www.wired.com/gadgets/gadgetreviews/magazine/16-09/ts_burningquestion